# Servolutions — full site text (llms-full.txt) Site: https://www.servolutions.com Language: en Generated: 2026-10-06 Canonical base URL: https://www.servolutions.com/ Index: https://www.servolutions.com/llms.txt Sitemap: https://www.servolutions.com/sitemap.xml Pages: 180 This file contains the main text of every page on this site as plain text (navigation, header and footer removed), one section per page with its source URL. Products: POPcon, POPcon PRO, MultiSendcon, ChangeSender, AddressView, MailSync Hub — email infrastructure software for Microsoft Exchange Server and Outlook by Servolutions IP Corporation. --- ## Servolutions — Email Infrastructure for Microsoft Exchange Source: https://www.servolutions.com/ Language: en 25+ years in production ### Email Infrastructure for Exchange, Done Right Production-grade add-ons for Microsoft Exchange Server. POP3/IMAP retrieval, intelligent SMTP routing, and Outlook tools — trusted by tens of thousands of IT admins worldwide. Download Free Trial Explore POPcon 30-day full-featured trial No credit card required Exchange 4.5 – 2019, + Exchange SE supported 25+ Years in production 80,000+ Exchange deployments Exchange 4.5 – 2019, + Exchange SE Full version coverage One-time Per-server license Product Suite ### Modular tools for Exchange — and beyond Each product solves a specific infrastructure problem. On-premise or cloud — buy only what you need. Flagship ### POPcon™ Download email from POP3 and IMAP mailboxes directly into Exchange Server. Automatically distributes messages to the right mailboxes — runs as a Windows service, 24/7. - POP3 & IMAP retrieval into Exchange - TLS 1.2 / 1.3 encryption - Windows service — no manual intervention - Per-server license, one-time fee Learn more Free Trial Advanced ### POPcon PRO™ Everything in POPcon, plus built-in antivirus, antispam filtering, and mail archiving. Parallel download threads for high-volume environments. - Built-in antivirus & antispam - Parallel download threads - Mail archiving & logging Learn more Cloud SaaS Under Development ### MailSync Hub Cloud-based IMAP sync with OAuth 2.0 authentication. Sync mailboxes to Microsoft 365 without managing on-premise connectors — subscription-based, hosted on Azure. - OAuth 2.0 / Modern Auth support - Microsoft 365 compatible - No on-premise software to install - Monthly or annual subscription Contact Us SMTP Routing ### MultiSendcon™ Route outbound Exchange email through different SMTP smart hosts based on sender address. Separate mail flows for different domains or departments. - Sender-based SMTP routing - Multi-domain support - Exchange send connector Learn more Outlook Add-in ### ChangeSender™ Choose which sender address your email goes out from, per message. Essential for Outlook users who manage multiple email identities. - Per-message sender selection - Multiple identity support - Native Outlook integration Learn more ### Proven in Production Running in Exchange environments since 2000. Every release tested against every supported Exchange version, from 4.5 through 2019. ### No Subscription Lock-In One-time per-server license for on-premise tools. No per-user fees, no forced renewals. Buy once and use it as long as your infrastructure needs it. ### Engineering-Level Support You reach the people who write the code. Direct access to developers who understand Exchange architecture — no ticket queues. Compatibility ### Supports Every Exchange Version From Exchange Server 4.5 through Exchange 2019 and Exchange Server SE, plus all Small Business Server (SBS) editions. Runs on Windows Server 2012–2025 and Windows 7–11 workstations. Exchange 4.5 Exchange 5.0 Exchange 5.5 Exchange 2000 Exchange 2003 Exchange 2007 Exchange 2010 Exchange 2013 Exchange 2016 Exchange 2019 Exchange Server SE All SBS Versions ### Ready to connect Exchange to the world? Download the full-featured 30-day trial. No credit card. No reinstallation required when you license — just enter your key. Download Free Trial View Pricing --- ## About Servolutions — Exchange Email Software Since 2000 Source: https://www.servolutions.com/about Language: en Founded 2000 ### Built by engineers, for IT administrators Servolutions IP Corporation builds email infrastructure software for Microsoft Exchange Server. We write software that runs quietly in the background, does exactly what it says, and keeps running for years without intervention. 25+ Years in business 2000 Year founded Exchange 4.5 – 2019 + SE Version coverage Germany Founded Our Story ### 25 years of Exchange infrastructure We started as Christensen Software in December 2000 with a single mission: solve real email infrastructure problems for IT administrators running Microsoft Exchange Server. In December 2025, we moved distribution to Servolutions IP Corporation — same team, same commitment, sharper focus. Our approach has always been the same: build software that installs in minutes, requires minimal configuration, and then runs reliably for years. No bloat, no cloud dependency, no subscription lock-in for on-premise tools. When something breaks, you reach the developers directly. Today our product suite spans POP3/IMAP connectors, outbound SMTP routing, and Outlook add-ins for Exchange Server — plus MailSync Hub, our new cloud sync product for Microsoft 365 environments. 2000 ### Founded Christensen Software founded in December 2000. First product: POPcon — a POP3 connector for Exchange Server. 2001–2010 ### Product expansion Added POPcon PRO, MultiSendcon, ChangeSender, and AddressView to the product suite. Built compatibility across Exchange 4.5 through 2010. 2011–2024 ### Continued reliability Maintained and extended compatibility with each Exchange release. Thousands of installations worldwide. Engineering-direct support policy established. 2025 ### Distribution moved to Servolutions IP Moved distribution to Servolutions IP Corporation in December 2025. Launched MailSync Hub for Microsoft 365 environments. Leadership ### Who builds Servolutions ### Claus Christensen Founder & CEO Claus has been developing software since 1980. He holds a computer science degree from Hamburg University and spent his early career as a hardware/software developer in scientific imaging and as head of electronics in aircraft engine manufacturing. He founded Servolutions in 2000 and has been building Exchange add-ons ever since. When you contact Servolutions support, there's a good chance you're talking directly to Claus. How We Work ### What we believe about software ### Reliability over features A product that runs for five years without incident is worth more than one with twenty checkboxes that occasionally fails. We build for uptime. ### Direct support, no queues When you have a problem, you talk to someone who can actually fix it. Not a tier-1 script reader — the engineers who wrote the code. ### Honest licensing On-premise products are one-time per-server license. No per-user fees, no forced upgrades, no subscriptions for software that runs on your hardware. ### Questions? Contact us directly. We're a small company. When you email us, you hear back from the people who built the product. Get in Touch Download Free Trial --- ## AddressView for Outlook — See the Recipient Email Address Source: https://www.servolutions.com/addressview Language: en ### AddressView for Outlook™ See which email address each message was actually sent to — right in your Outlook inbox. When you have multiple email addresses in Exchange, Outlook only displays your name as the recipient. AddressView shows the actual recipient address above the standard email fields. Download Free Trial Prices & Shop ### Features - Displays the recipient address instead of just your name - Works with all Microsoft Outlook versions for Windows - One-time purchase, no annual fees ### 30-Day Free Trial Download, install, and test AddressView free for 30 days. Purchase a license key to unlock unlimited use — no reinstallation required. Download AddressView --- ## Download AddressView v1.72 for Outlook — 30-Day Trial Source: https://www.servolutions.com/addressview/download Language: en ### Download AddressView for Outlook Current version: AddressView v1.72 Download AddressView v1.72 ### Trial & Licensing Free 30-day trial — test the full product without any restrictions. Order a license code to remove the 30-day limit without reinstalling. Order license --- ## Configure AddressView Source: https://www.servolutions.com/addressview/help/configure Language: en ### Configure AddressView Access the configuration dialog from Outlook: Add-Ins > AddressView > Configure . ### License Code Enter your license code here to activate AddressView beyond the 30-day trial period. No reinstallation is required — the license takes effect immediately. Purchase a license from the web shop . ### My Email Addresses Enter a list of your own email addresses. AddressView uses this list to identify which addresses are “yours” when displaying the sent-to information above email messages that have multiple recipients (TO, CC, BCC fields). Without this list, AddressView cannot distinguish your addresses from those of other recipients. ### Load from ActiveDirectory If your computer is joined to an Active Directory domain, click this button to automatically populate your email addresses from the directory server. This is the quickest way to populate the list in a corporate environment. ### Sent-to Dialog Background Color Customize the background color of the “Sent to” information bar displayed above email headers. Change this from the default system dialog color to make it more visible or to match your preferences. --- ## AddressView Version History Source: https://www.servolutions.com/addressview/history Language: en ### AddressView Version History v1.71 — Now installs without admin privileges under normal user accounts. v1.70 — Supports Italian, Spanish, Brazilian Portuguese, and French languages. Bugfix: Solved “null reference” problem in Outlook 2013. v1.60 — Displays addresses in reading pane of Outlook 2013. Allows import of recipient addresses from email. Shows version number in configuration dialog. v1.50 — First public release after beta phase. --- ## AddressView System Requirements Source: https://www.servolutions.com/addressview/requirements Language: en ### AddressView System Requirements ### Operating System Windows 10 x86/x64, Windows 8.1 x86/x64, Windows 8 x86/x64, Windows 7 x86/x64, Windows Vista, Windows XP, Windows Server 2012, 2008, 2003, 2000. ### Email Client Compatible with all current Outlook versions: Outlook 2013™, Outlook 2010™, Outlook 2007™, Outlook 2003™. ### Hardware No special requirements. --- ## AddressView Support — Contact and Online Help Source: https://www.servolutions.com/addressview/support Language: en ### AddressView Support Email and phone support is included with all our products. We take pride in providing reliable, responsive support to all our customers. Contact: support@servolutions.com ### Online Help Press F1 in the application for built-in help with the configuration dialog. --- ## AttackTracer — Discontinued Source: https://www.servolutions.com/attacktracer Language: en ### AttackTracer Notice: AttackTracer has been discontinued and is no longer available for download. Thank you to everyone who used it over the years. ### What Was AttackTracer? AttackTracer was a free tool that scanned Windows server logs for traces of hacking attempts. It checked for bot and hacker attacks against Remote Desktop (RDP), FTP, and SQL-Server services. It helped server administrators identify whether their systems were being targeted by automated login attacks. ### Features (Historical) - Read hacking events from Remote Desktop, SQL-Server, FTP, and Filezilla-FTP logs - Showed the country of origin for attacking IPs - Listed all attacks grouped by IP address - Could send email alerts with attack details --- ## BotFence — Discontinued Source: https://www.servolutions.com/botfence Language: en ### BotFence Notice: BotFence has been discontinued and is no longer available for download or purchase. ### What Was BotFence? BotFence automatically blocked IP addresses that launched hacking attempts on Windows server services (Remote Desktop, FTP, SQL-Server) using the Windows firewall. It ran as a background service and dynamically blocked attacking IP addresses without manual intervention. ### Features (Historical) - Dynamically blocked IP addresses of attacking bots in the Windows firewall - Monitored Remote Desktop, SQL-Server, WordPress, FTP, and Filezilla-FTP - Showed the country of origin for attackers - Notified the administrator by email about blocked hacking attempts - Sent daily or weekly summaries of blocked attacks - Detected botnet attacks — coordinated attacks from multiple machines --- ## ChangeSender — Change the Sender Address in Outlook Source: https://www.servolutions.com/changesender Language: en Outlook Add-in ### ChangeSender ™ Exchange Send-As for Outlook Choose which sender address your emails go out from — per message, in Outlook. Automatic reply address matching, signature switching, and keyboard shortcuts. Essential for anyone managing multiple email identities in Exchange. Download Free Trial Prices & Licensing 30-day full-featured trial — no credit card Per-seat license, one-time fee Exchange 2000 – 2019, + Exchange SE Features ### Everything you need to manage multiple email identities in Outlook ### Per-Message Sender Selection A send-as dropdown appears directly in the Outlook mail form. Select any configured address before sending — no extra steps, no menus to hunt through. ### Automatic Reply Address Matching When you reply to an email, ChangeSender automatically sets the sender address to match the address the original email was received on. No manual selection needed. ### Email Signature Switching Configure a different Outlook signature for each sender address. ChangeSender automatically switches the signature when you change the send-as address. ### Per-Address Sent Items Folders Optionally save sent mail to different Outlook folders depending on which sender address was used. Keep your sent items organized by identity. ### Keyboard Shortcuts Assign keyboard shortcuts (CTRL-1, CTRL-2, etc.) to your most-used sender addresses for rapid switching without lifting your hands from the keyboard. ### Administrator Controls Administrators can restrict which sender addresses each user may choose from, or lock specific users to a fixed sender address — configurable via the server component. ### Shared Address Support Multiple users can send from the same shared address (sales@, support@, info@) without the message appearing as 'sent on behalf of'. Full name control included. ### Terminal Server / Citrix Available in a separate Terminal Server / Citrix edition for multi-user environments. A DisableTool utility lets administrators control which users see the add-in. Compatibility ### Outlook & Exchange versions ChangeSender works with any combination of supported Outlook and Exchange Server versions. Both client (Outlook add-in) and server (Exchange component) installers are included. Exchange Server Exchange 2000 Exchange 2003 Exchange 2007 Exchange 2010 Exchange 2013 Exchange 2016 Exchange 2019 Exchange Server SE Outlook Outlook 2007 Outlook 2010 Outlook 2013 Outlook 2016 Outlook 2019 Outlook 2021 Microsoft 365 Apps Support & FAQ ### Common questions ### ChangeSender is installed but the sender address isn't changing. What's wrong? The most common cause is that the Outlook add-in isn't loading. Check that ChangeSender appears in Outlook's Add-ins list (File > Options > Add-ins) and is enabled. If it's listed as 'inactive' or 'disabled', re-enable it. Also confirm the server component is running and can communicate with the Exchange server. ### How do I restrict which send-as addresses a user can choose? Install the server component on your Exchange server. Use the ChangeSender Server Configuration tool to define allowed sender addresses per user or group. Users will only see the addresses you configure for them in their Outlook dropdown. ### Can two users share a single send-as address? Yes. Configure the shared address (e.g. sales@company.com) in the server component and assign it to multiple users. Each user's ChangeSender will show that address as an option. Sent mail will show the shared address, not 'on behalf of'. ### How do I deploy ChangeSender to all users at once? Use the 'For all users' installer for terminal server / Citrix environments, or deploy via Group Policy or your software deployment tool. After installation, use the ChangeSenderDisable tool to disable the add-in by default, then enable it selectively for users who need it. ### Does ChangeSender work on Exchange 2019 / Exchange SE? Yes. ChangeSender is compatible with Exchange 2000 through 2019 and Exchange Server SE, with Outlook 2007 through the current Office versions. ### The signature isn't switching automatically. How do I set it up? The signature names in Outlook must match the sender address name exactly (e.g. if your address is john@company.com, the signature should be named 'john@company.com'). Once the names match, ChangeSender will switch signatures automatically when you change the send-as selection. ### Can I set a default sender address for new emails? Yes. In the ChangeSender configuration, you can set a different default send-as for new emails vs. replies. This is useful when you always want new emails to go out from a specific address, but want replies to use the automatic match. Need help? Email support directly — you'll reach the engineers who wrote the software. Installation Guide Release History ### Version history 2016 v3.25 November 07, 2016 Images in signatures now inserted correctly from external files. 'Send as' label no longer printed when printing sent emails. v3.24 October 25, 2016 Log files blocked by other programs no longer halt the ChangeSender add-in. v3.23 August 19, 2016 Speed improvement by preventing exceptions from header scanning for empty header fields. v3.22 May 09, 2016 Finds original recipient for replies in difficult cases with multi-line TO: or CC: headers. 2015 v3.21 October 21, 2015 Supports inline replies and forwards in Outlook 2013/2016 reading pane. Bugfix for outbox emails switching to 'edited' mode. v3.20 October 16, 2015 Outlook 2016 support. v3.19 July 08, 2015 Default fixed sender address now applies when sending from external applications like Adobe Acrobat. v3.18 July 02, 2015 X-Sender header support. Stability improvements with antivirus blocking log files. v3.16 March 23, 2015 Bugfix for address change with x64 installations. Sent-items folder move issues resolved. 2014 v3.11 August 08, 2014 Picks up signatures from localized Outlook versions. v3.10 July 25, 2014 SentItems folder to public/other user folders. CTRL+1,2,3,4 view switching restored. 2013 v3.00 October 24, 2013 New: Individual sent-items folders per sender address. Keyboard shortcuts CTRL-1, CTRL-2, etc. Automatic signature change in all Outlook 2013 versions. 2012 v2.96 December 04, 2012 Outlook 2013 support. v2.95 November 27, 2012 Terminal server/Citrix installation support. v2.94 November 14, 2012 Individual email signatures selectable without edit rights. v2.92 April 19, 2012 Email signatures selectable individually for each address. v2.90 January 28, 2012 Configurable default Send-as for NEW emails vs. Replies. Reply-To header modification. Multi-domain ActiveDirectory support. 2011 v2.83 November 09, 2011 Modifies Reply-to and Return-Path header fields. Auto-signature switching bugfix. Terminal server/Citrix version added. v2.80 October 07, 2011 Address change now automatically changes email signature. v2.70 September 27, 2011 Configuration via .cfg file. Faster Outlook startup. Network-mapped drive support. 2010 v2.50 December 04, 2010 Support for computers not in the same ActiveDirectory domain. x64 Outlook on Windows 7 support. v2.00 August 06, 2010 Outlook 2010 support. v1.80 February 09, 2010 First published version after beta phase. --- ## ChangeSender Demo Source: https://www.servolutions.com/changesender/demo Language: en ### ChangeSender Demo Our demo video shows ChangeSender in action within Microsoft Outlook. The short screencast walks you through the key features and demonstrates how easy it is to switch the sender address for outgoing emails. ### What the Demo Covers - How to select a different sender address before sending an email - Automatic sender selection based on the recipient domain - Configuration of sender addresses and rules in the ChangeSender settings - How ChangeSender works transparently with Microsoft Exchange Server The demo video was originally hosted as an embedded screencast. The video is no longer available inline, but you can try ChangeSender yourself by downloading the free trial: Download ChangeSender If you manage multiple email addresses or send on behalf of different departments, ChangeSender makes the process seamless. Feel free to share the download link with colleagues who might benefit from the tool. --- ## ChangeSender Download v3.25 — Server + Outlook Add-in Source: https://www.servolutions.com/changesender/download Language: en ### Download ChangeSender Current version: ChangeSender v3.25 Free 30-day trial. Purchase a license code to remove the trial limitation — no reinstallation required. ### Two-Component Installation ChangeSender requires both a server component and an Outlook add-in. Install the server component first. ### Client Component (Outlook Add-in) - Individual user: SetupChangeSenderEN.exe — install as the user (not Administrator) - For-all-users (Terminal Server/Citrix): SetupChangeSenderEnTS.exe — install as Administrator ### Server Component - Exchange 2013/2010/2007: ChangeSenderServerSetup.exe - Exchange 2003/2000: ChangeSenderServer2003Setup.exe Installation guide · Version history · Order license --- ## ChangeSender Features: Send-As Addresses in Outlook Source: https://www.servolutions.com/changesender/features Language: en ### ChangeSender Features - Automatic Sender Selection: Automatically selects the right sender address when replying to emails, using the original recipient's address. - Send-As Selection Box: Easy selection of sender addresses for new emails via a “send as” selection box in Outlook. - Dynamic Email Signatures: Email signatures change automatically according to the selected sender address. - Sent Items Folder Management: Choose to have sent emails moved to specific Sent-items folders matching the chosen address, or keep them in the normal sent-items folder. - Keyboard Shortcuts: CTRL-1, CTRL-2, etc. for quick address selection. - Multiple Users, Single Address: Multiple users can send from the same sender address (e.g. sales@company.com) without having to use a fixed name string. - Configurable Sender Appearance: Fully configurable as “Any name” for each individual email address. Does not show up as “sent on behalf of…” - Simple Installation: No need to juggle additional email accounts or groups. - Administrative Controls: Administrator can restrict or allow user choices for sender addresses. - Third-Party App Support: Also works when emailing from third-party applications and Windows ‘Send to’. Not sure whether you need Send As, Send on Behalf or an alias? The guide Send As vs Send on Behalf vs sending from an alias defines the three and shows where an add-in comes in. ### Compatibility Exchange 2016, 2013, 2010, 2007, 2003, 2000 and Outlook 2016, 2013, 2010, 2007. Download Trial --- ## ChangeSender Version History Source: https://www.servolutions.com/changesender/history Language: en ### ChangeSender Version History v3.25 (November 07, 2016) — Images in signatures now inserted correctly from external files. “Send as” label no longer printed when printing sent emails. v3.24 (October 25, 2016) — Log files blocked by other programs no longer halt the ChangeSender add-in. v3.23 (August 19, 2016) — Speed improvement by preventing exceptions from header scanning for empty header fields. v3.22 (May 09, 2016) — Finds original recipient for replies in difficult cases with multi-line TO: or CC: headers. v3.21 (October 21, 2015) — Supports inline replies and forwards in Outlook 2013/2016 reading pane. Bugfix for outbox emails switching to “edited” mode. v3.20 (October 16, 2015) — Outlook 2016 support. v3.19 (July 08, 2015) — Default fixed sender address now applies when sending from external applications like Adobe Acrobat. v3.18 (July 02, 2015) — X-Sender header support. Stability improvements with antivirus blocking log files. v3.16 (March 23, 2015) — Bugfix for address change with x64 installations. Sent-items folder move issues resolved. v3.11 (August 08, 2014) — Picks up signatures from localized Outlook versions. v3.10 (July 25, 2014) — SentItems folder to public/other user folders. CTRL+1,2,3,4 view switching restored. v3.00 (October 24, 2013) — New: Individual sent-items folders per sender address. Keyboard shortcuts CTRL-1, CTRL-2, etc. Automatic signature change in all Outlook 2013 versions. v2.96 (December 04, 2012) — Outlook 2013 support. v2.95 (November 27, 2012) — Terminal server/Citrix installation support. v2.94 (November 14, 2012) — Individual email signatures selectable without edit rights. v2.92 (April 19, 2012) — Email signatures selectable individually for each address. v2.90 (January 28, 2012) — Configurable default Send-as for NEW emails vs. Replies. Reply-To header modification. Multi-domain ActiveDirectory support. v2.83 (November 09, 2011) — Modifies Reply-to and Return-Path header fields. Auto-signature switching bugfix. Terminal server/Citrix version added. v2.80 (October 07, 2011) — Address change now automatically changes email signature. v2.70 (September 27, 2011) — Configuration via .cfg file. Faster Outlook startup. Network-mapped drive support. v2.50 (December 04, 2010) — Support for computers not in the same ActiveDirectory domain. x64 Outlook on Windows 7 support. v2.00 (August 06, 2010) — Outlook 2010 support. v1.80 (February 09, 2010) — First published version after beta phase. --- ## How to Install ChangeSender on Exchange and Outlook Source: https://www.servolutions.com/changesender/installation Language: en ← ChangeSender ### How to install ChangeSender ChangeSender actually consists of two parts: the server component and the client component (the Outlook add-in). The Outlook add-in is the part that actually displays the “Send-as” selection box in each e-mail dialog. It takes that information and — while it can’t actually change the sender, because Exchange would prohibit that — it does add this information to a special field in the email. The Outlook component must be installed on the client computer of each user who needs to use the Send-as function. The server component then takes that information out of the special field and changes the sender to the one selected in the Outlook add-in after Exchange processed the email. This component is installed only once, on the Exchange server. In addition to this main job, the server component also includes a small utility to restrict the usage of email addresses by the individual users. This “Configure ChangeSender and Client Restrictions” tool allows the Administrator to specify, for each user, whether that user can choose an address: - only from their email addresses configured in the Active Directory (this is the default), or - freely edit the list of available addresses: add new addresses or remove addresses originally present in the AD so they are no longer available for the user to choose from, or - add any address they like with no restrictions. Both parts – the server component on the Exchange server and the client component on the individual user’s systems – need to be installed for ChangeSender to work. ### 1. Installing the server component To install the server component please download the self-extracting installer and execute it on the server while being logged in as Administrator. The installer will install these parts: - The Exchange outgoing email handler that actually changes the address. - The “Configure ChangeSender and Client Restrictions” tool for configuring which addresses can be used by the individual users. The installation usually does not require a reboot, except if the “Exchange transport” service is very busy during installation and is thus kept from restarting. After installation you can use the “Configure ChangeSender Client Restrictions” tool to control usage of email addresses by your users by generating a configuration file that is then imported by the ChangeSender Outlook add-in on the client. ### 2. Installing the Outlook add-in To install the client component please download the ChangeSender client component self-extracting installer and execute it on the client’s computer. It is best to do this with Outlook not running during the install. If you kept Outlook running during the install, you need to shut that down and restart it again to see the new “Send-as” box in the email forms: As you can see in this screenshot of the Outlook 2010 new email form, a new “Send as” toolbar appears in all email forms. The default address is displayed in a selection box and you can use the arrow symbol next to that to show and select from the other possible email addresses. The properties symbol next to the send-as selection box allows you to administrate the ChangeSender add-in: You can select which of the available email addresses (read from the Active Directory) should show up in the selection box and also edit the “Name” part of the address. By default Exchange will name all email addresses the same, usually “First-Name Last-Name”. But with ChangeSender you can have different name parts for different addresses – like “Sales Team, Company Name” for the sales@yourcompany.com address and just “Company Name” for the info@yourcompany.com. In those cases where the Administrator allowed the use of any address, the “Add” button shows up in the configuration and you can enter additional email addresses here. After configuring the ChangeSender client you can immediately start to use it. Just select an address and send off the email as usual. --- ## ChangeSender System Requirements Source: https://www.servolutions.com/changesender/requirements Language: en ### ChangeSender System Requirements ### Outlook Add-in (Client) Operating System: Windows 10, 8.1, 8, 7, Vista, XP, Windows Server 2008, 2003, 2000 Outlook: Outlook 2016™, Outlook 2013™, Outlook 2010™, Outlook 2007™ ### Server Component Windows Server: Windows 2016 Server (all releases), Windows 2012 Server (all releases), Windows 2011 SBS x64, Windows 2008 SBS x64, Windows 2008 Server x86/x64, Windows 2003 Server x86/x64, Windows 2000 Server Exchange: Exchange Server 2013™, Exchange Server 2010™ (incl. SBS), Exchange Server 2007™ (incl. SBS), Exchange Server 2003™ (incl. SBS), Exchange Server 2000™ (incl. SBS) ### Hardware No special requirements. 10 MB disk space. --- ## ChangeSender Support — Contact, Install Guide, FAQ Source: https://www.servolutions.com/changesender/support Language: en ### ChangeSender Support Email and phone support is included with all our products. Contact: support@servolutions.com ### Installation Help See the ChangeSender installation guide for step-by-step setup instructions. ### Frequently Asked Questions - ChangeSender installed correctly but the sender address appears unchanged - How can I restrict my users’ choices for the Send-As address? - How can I use the same sender address for two Exchange mailboxes? - How can I disable the Add-in for all users by default? --- ## Contact Servolutions — Direct Support from the Developers Source: https://www.servolutions.com/contact Language: en ### Talk to the team that wrote the code We're a small company. When you contact us, you're talking to the people who build and maintain the software — not a support tier. ### Email us Choose the right address and we'll get back to you quickly. All inquiries handled directly by the team. Support support@servolutions.com Technical issues, configuration help, bug reports Sales sales@servolutions.com Licensing questions, volume purchases, MailSync Hub General info@servolutions.com General questions and enquiries Feature Requests wishlist@servolutions.com Tell us what you want to see in future versions 🇩🇪 ### Europe +49 40 209338822 Christensen Software GmbH Bei den Mühren 1 20457 Hamburg Germany 🇺🇸 ### United States +1 (302) 857-0301 Eastern Time. If unavailable, email support@servolutions.com . Servolutions IP Corporation 8 The Green STE R Dover, DE 19901 United States Before You Write ### Common questions ### Where do I find my license key? License keys are emailed to the address used at purchase. If you've lost your key, email support@servolutions.com with your order details. ### Where do I download the software? All downloads are on the Downloads page . The trial version is the same installer as the full version — enter your license key to unlock it. ### Does my license cover upgrades? Major version upgrades are typically paid; minor updates within a version are free. Contact us with your license details for specifics. ### Can I run on multiple servers? Licenses are per-server. Each Exchange Server installation requires a separate license. Contact sales@servolutions.com for volume pricing. ### What Exchange versions are supported? POPcon and MultiSendcon support Exchange 4.5 through Exchange 2019 + SE, including all SBS versions. See the individual product pages for full compatibility details. ### I'm on Microsoft 365 — which product? For Microsoft 365 / Exchange Online environments, see MailSync Hub — our cloud-based IMAP sync with OAuth 2.0 authentication. --- ## Disclaimer — Servolutions Source: https://www.servolutions.com/disclaimer Language: en ### Disclaimer ### Content The author reserves the right not to be responsible for the topicality, correctness, completeness, or quality of the information provided. ### Referrals and Links The author is not responsible for any contents linked or referred to from these pages — unless he has full knowledge of illegal contents. ### Copyright The copyright for any material created by the author is reserved. Any duplication or use of objects such as diagrams, sounds, or texts in other electronic or printed publications is not permitted without the author's agreement. ### Privacy The input of personal or business data (email addresses, name, addresses) takes place voluntarily. ### Legal Validity This disclaimer is to be regarded as part of the internet publication which you were referred from. © 2000–2026 Servolutions IP Corporation --- ## Downloads — Servolutions Email Infrastructure Software Source: https://www.servolutions.com/download Language: en ### Download & Try Free for 30 Days All products are fully functional during the trial — no feature restrictions. Enter your license key to unlock permanently. No reinstallation required. No registration required No credit card 30-day full trial Flagship POPcon™ Exchange POP3 / IMAP Connector Connects external POP3 and IMAP mailboxes to Exchange Server. Automatic mail distribution, Windows service, TLS 1.2/1.3. Latest: v4.10.x Download Product page POPcon PRO™ Advanced Exchange POP3 / IMAP Connector Everything in POPcon, plus built-in antivirus, antispam filtering, rule-based distribution, mail archiving, and parallel download threads. Latest: v4.10.x Download Product page MultiSendcon™ Sender-Based Exchange SMTP Routing Routes outbound Exchange email through different SMTP smart hosts based on sender address. Per-sender authentication, unlimited routing rules. Latest: v3.3.x Download Product page ChangeSender™ Outlook Send-As Add-in Choose which sender address your Outlook emails go out from, per message. Automatic reply address matching and email signature switching. Latest: v3.25 Download Product page ### Same installer, trial or licensed Download once. Enter a license key to unlock full permanent use. No separate installers to manage. ### Exchange 4.5 – 2019, + Exchange SE Compatible with every Exchange Server version released since 1996, including all SBS versions. ### Direct support from developers Need help installing? Email support@servolutions.com and you'll hear back from the engineers who wrote the software. --- ## Exchange POP3 Connector — POP3/IMAP Mail into Exchange Source: https://www.servolutions.com/exchange-pop3 Language: en ### Exchange POP3 Connector Need to connect your Microsoft Exchange Server to POP3 or IMAP mailboxes? POPcon downloads emails from internet mailboxes and distributes them to Exchange mailboxes based on recipient information found in the mail headers. ### Our Products ### POPcon Connects Microsoft Exchange Server to POP3 and IMAP mailboxes. Downloads emails and distributes them to the appropriate Exchange users based on recipient information. Compatible with Exchange 5.5 through 2019 + SE, all SBS versions. Learn more ### POPcon PRO All standard POPcon features plus integrated antivirus scanner, antispam filtering via blacklist servers, and a programmable rule-based email distribution engine. Antivirus signatures update automatically. Learn more ### Recent Support Topics - Connect to Gmail with modern authentication (OAuth2) - Connect to Microsoft 365 / Outlook with OAuth2 - How to manually create the Send Connector in Exchange - Does Exchange Server have a built-in POP3 connector? - POP3 retrieval or MX record to Exchange: which to choose? - Exchange mail flow guides — POP3 retrieval, send connectors, sender addresses, OAuth2 Download Trial Prices & Shop --- ## Exchange Send-As Tool — ChangeSender Source: https://www.servolutions.com/exchange-send-as-tool Language: en ### Exchange Send-As Outlook Add-in: ChangeSender ChangeSender adds a critical capability to Microsoft Outlook with Exchange Server: it lets users send email as any of their email addresses — or even shared group addresses — without the limitations of Active Directory. ### The Problem Without ChangeSender, Exchange always sends from the user’s fixed default email address, even when replying to emails received on an alternative address. Exchange also does not allow multiple users to share a department or company-wide email address (such as sales@company.com). ChangeSender solves both problems. ### Features - Automatically selects the correct send-as address when replying (uses the original recipient address) - Easy selection of send-as addresses for new emails via a sender address dropdown in Outlook - Multiple users can send from the same address (sales@, support@, info@) - Sender appears as “Any Name ” — does NOT show as “sent on behalf of” - Simple installation and administration - Administrator can restrict or allow user choices for sender address - Compatible with Exchange 2000–2019 and Outlook 2000–2024 Download Trial Prices & Shop Full ChangeSender product page → Background: Send As, Send on Behalf, shared mailbox or add-in — the four ways to choose the From address on Exchange on-premises, compared . --- ## Freeware Utilities — Servolutions Source: https://www.servolutions.com/freeware Language: en ### Servolutions Freeware Utilities Small utilities and testing tools we have developed that may be useful for a broader audience. Note: These tools are provided as-is with no warranties. Use at your own risk. ### RemoveWhitespaceFromAddRemovePrograms A small utility that cleans up the Windows registry when large gaps of whitespace appear in the Add/Remove Programs control panel. This issue is caused by badly formatted “DisplayedIcon” entries in the uninstall area of the registry or by a corrupt icon file. - Fixes whitespace gaps in Add/Remove Programs - Executable is only 32 KB - Requires .NET Framework - Free to download, use, and distribute --- ## Exchange Mail Flow Guides — POP3, Send Connectors, OAuth2 Source: https://www.servolutions.com/guides Language: en ### Exchange Mail Flow Guides These guides answer the questions Exchange administrators ask about getting mail into and out of an on-premises Exchange Server: POP3/IMAP retrieval, send connectors and smart hosts, sender addresses in Outlook, and OAuth2 for Microsoft 365 and Gmail. Each guide opens with the direct answer, cites Microsoft Learn wherever we rely on Microsoft’s documented behaviour, and points to a product only where a product is part of the answer. Guides are added one at a time. Until a guide exists for a question, the lists below point to the pages that already cover it. Updated on 2026-09-12 ### Inbound: POP3 and IMAP retrieval into Exchange Getting mail that arrives in provider mailboxes (IONOS, Strato, GMX, Gmail, Microsoft 365) into on-premises Exchange mailboxes, and the questions that follow once it works. - Does Exchange Server have a built-in POP3 connector? — the POP3 service vs a POP3 connector, why only SBS 2008/2011 had one, and what replaces it on Exchange 2013 to SE. - The SBS 2008/2011 POP3 Connector: what it did, its limits, and the replacement — feature-by-feature comparison with a current connector and the migration steps when you leave SBS. - How to download POP3 and IMAP mailboxes into Exchange 2016, 2019 and SE — the four steps: accepted domain, receive connector, connector accounts, first test, plus the errors a fresh setup runs into. - Catch-all (multidrop) mailbox vs one POP3 mailbox per user — which routes correctly, where BCC and mailing lists break, what happens to unknown recipients, and how to mix both. - POP3 or IMAP for retrieving provider mailboxes into Exchange? Ports, TLS, leave-on-server and OAuth2 — the two protocols as a connector uses them, why the encryption setting must match the port (TLS on 995/993, STARTTLS on 110/143), the delete / leave-on-server options, and where Microsoft 365 and Gmail decide for IMAP. - POP3 retrieval or MX record to Exchange: when a connector is the right choice and when it is not — what direct SMTP delivery requires (public DNS, inbound port 25, your own spam filtering), what happens to mail while Exchange is down in either design, and the order in which to switch from retrieval to the MX record. - Where to install a POP3/IMAP connector: on the Exchange server, a member server, or a workstation — what the connector needs at every placement (outbound POP3/IMAP, SMTP to one receive connector), how the three placements differ in firewall path, receive connector scope and antivirus exclusions, and the checks when it downloads fine but cannot reach Exchange. - Exchange Server SE (Subscription Edition) and POP3/IMAP mailbox retrieval: what changes, what does not — SE RTM is code equivalent to Exchange 2019 CU15 and still has no built-in POP3 connector; what to check on the connector after an in-place upgrade, and the order of work when Exchange 2016 or 2013 means a new server. - POP3/IMAP over TLS for mail retrieval: ports 995 and 993, STARTTLS vs implicit TLS, and “-ERR Command is not valid in this state” — implicit TLS on 995/993 vs STARTTLS on 110/143 as Microsoft documents them for Exchange Server and Exchange Online, what Microsoft 365 and Gmail expect, why STLS on port 995 is refused, the four encryption values in the connector, TLS versions, and the SMTP twins 504 5.7.4 and 530 5.7.0. - Exchange POP3 connector — what a POP3/IMAP connector does and which Exchange versions it serves. - Configure Exchange 2013 / 2016 to receive mail from POPcon — the receive-connector setup; guides for Exchange 2010 , 2007 and 2003 sit beside it. - Which Exchange versions and SBS editions does POPcon work with? - Why does a connector need to know the accepted domains? — the catch-all mailbox question. - Mailing-list mail is not distributed correctly and BCC recipients do not receive the email — the two classic catch-all follow-ups. - Only messages under 10 MB come through and how to raise the Exchange size limit . - Non-delivery reports for unknown users behind a POP3 connector. - Could not reach Exchange SMTP server — port 25 blocked . ### Outbound: send connectors and smart hosts Routing outgoing mail from Exchange through provider relays, including several smart hosts and authentication per sender. - Exchange send connectors route by recipient domain, not sender — how to route outbound mail by sender address anyway — how connector selection works, why two * connectors do not help, and the three options that do. - Multiple smart hosts in Exchange 2016/2019: per recipient domain (built in) and per sender (with a relay) — both setups step by step, the commands to verify them, and a comparison table. - Using IONOS, Strato or GMX as the smart host for Exchange: why the sender must match the login — what IONOS enforces since January 2024 (sender domain = login mailbox, no empty sender), the symptom table, and one relay session per sender domain. - Exchange: “A matching connector cannot be found to route the external recipient” — causes and fix — why mail lands in the Unreachable queue, the five connector settings behind it, and the commands to check and resubmit. - Hosting several companies or domains on one Exchange Server — accepted domains and email address policies per company inbound, one provider relay and login per sender domain outbound, a worked example with two providers, and what stays shared. - Multiple send connectors for Exchange — routing by sender address to different smart hosts. - Creating the send connector in Exchange manually . - 504 5.7.4 Unrecognized authentication type — when relaying through the Office 365 SMTP servers fails. - IONOS blocks non-delivery reports and out-of-office messages — the empty-sender rule at the IONOS relay. ### Sender address in Outlook Letting Outlook users choose the From address per message on Exchange on-premises, and keeping that choice under control. - How Outlook users can choose a different From address on Exchange on-premises — Send As, Send on Behalf, a shared mailbox or an add-in, compared. - Send As vs Send on Behalf vs sending from an alias — the three terms defined, what the recipient sees, where replies land, and why alias sending exists only in Exchange Online. - Change the sender address in Outlook — per-message sender selection for Exchange users. - Using the same sender address for two Exchange mailboxes . - Restricting which Send-As addresses users may choose . ### Authentication and SMTP errors Modern authentication for the mailboxes a connector reads, and the SMTP responses Exchange returns when a connector submits mail. - Basic authentication is gone: fetching a Microsoft 365 mailbox by IMAP or POP3 with OAuth2 into Exchange — what Microsoft switched off, how a service keeps a token alive without a password, the seven setup steps, and the symptoms behind “the password is correct but it keeps asking”. - Fetching Gmail and Google Workspace mail into Exchange over IMAP with OAuth2 — what Google switched off for Workspace and personal accounts, why an app password is not the answer, the eight setup steps on imap.gmail.com port 993, and IMAP vs POP3 at Google. - Exchange SMTP error codes explained: 421 4.4.1, 421 4.4.2, 451 4.7.0, 452 4.3.1, 530 5.7.1, 550 5.7.1 and more — every reply a connector sees when it submits mail to Exchange, in one table per class: what it means, the usual cause, the fix and the knowledge base article with the commands. - “550 5.7.1 Unable to relay” when a connector submits to Exchange — what Exchange checks before it refuses a recipient, why the missing accepted domain is the usual cause, which receive connector answers, and Microsoft’s dedicated relay connector for hosts that must send to external recipients. - Messages over 10 MB are not arriving: size limits between the POP3 connector and Exchange — the organization, receive connector and mailbox limits with Microsoft’s defaults, which one stops connector mail and whether the sender is told, and how to raise them and resend what waits in the TOOLARGE folder. - NDRs for external senders behind a POP3 connector — unknown recipients, oversized mail and out-of-office replies: when Exchange generates the non-delivery report, when the message goes to the postmaster or stays in the queue instead, and why a provider that refuses empty senders stops the report on its way out. - OAuth2 for Microsoft 365 and Outlook.com mailboxes — the walkthrough with screenshots. - Gmail with modern authentication (OAuth2) . - 530 5.7.0 Must issue a STARTTLS command first . - 530 SMTP authentication is required . - 550 5.7.1 Unable to relay . - 421 4.4.2 Message submission rate exceeded . - 421 4.4.1 Connection timed out . - 452 4.3.1 Insufficient system resources . - 451 4.7.0 Temporary server error (PRX) . Everything else is in the knowledge base . If your question is not covered, ask support — unanswered questions are how the next guide gets chosen. --- ## Catch-all mailbox vs one POP3 mailbox per user for Exchange Source: https://www.servolutions.com/guides/catch-all-mailbox-vs-individual-pop3 Language: en Exchange mail flow guides › Inbound: POP3 and IMAP retrieval ### Catch-all (multidrop) mailbox vs one POP3 mailbox per user — which works better with Exchange? A catch-all (multidrop) mailbox receives every message for a domain in one POP3 account and relies on the connector reading recipient headers to route each message to the right Exchange mailbox; individual mailboxes make routing exact but cost one account per user. In practice the choice is decided by two things: whether your provider preserves the original recipient in the message headers, and how many users and mailing lists you have. This guide compares both setups and shows how POPcon handles each. Updated on 2026-09-15 Both models end in the same place: a connector service downloads the provider mailbox on a schedule and submits each message to Exchange over SMTP (the setup is in How to download POP3 and IMAP mailboxes into Exchange 2016, 2019 and SE ). The difference is how the connector learns who the message is for. ### Definitions Catch-all mailbox. The provider delivers mail for anyone@yourcompany.com into a single POP3 or IMAP account. The connector examines the headers of every downloaded message (To:, CC: and a list of non-standard fields the providers add) to determine the intended recipients, and delivers each message to the corresponding Exchange mailbox. Some providers call this a multidrop, domain or wildcard mailbox. Individual (single-user) mailbox. The provider keeps one POP3 or IMAP account per address. The connector delivers everything from that account to one Exchange recipient you configure, regardless of the addresses in the message headers. ### Catch-all vs individual mailboxes: the comparison | Criterion | Catch-all (multidrop) mailbox | One mailbox per user | | --- | --- | --- | | Routing accuracy | Depends on the headers the provider preserves; correct for normal To:/CC: mail, uncertain for BCC and lists | Exact: every message goes to the configured recipient | | BCC recipients | Only routable if the provider records the original recipient in a header such as X-Original-To or Delivered-To; otherwise unroutable | Always delivered | | Mailing lists | The list server often removes the subscriber address; such mail lands with the postmaster | Always delivered; the list subscription can get its own mailbox | | Mail sent to several of your users | The provider may store one copy per recipient; the connector must recognise the copies and deliver once | Each user’s mailbox holds their own copy | | Recipients outside your domain in the same message | Must be filtered out through the accepted recipient domains list, or Exchange bounces them | Not an issue: the recipient is fixed | | Unknown recipients in your domain | The connector must decide: re-route to the postmaster, or let Exchange send a non-delivery report | Cannot occur: the provider only accepts existing addresses | | Accounts to manage | One account, no change when users join or leave | One account per user, created at the provider and in the connector | | Cost at the provider | One mailbox | One mailbox per user, depending on the provider’s plan | | Configuration in the connector | One account with the accepted recipient domains and, optionally, a re-route address | One account per user with the target Exchange address | ### Why catch-all routing can fail: BCC, mailing lists and stripped headers A catch-all mailbox only works as well as the headers the provider hands over. Two cases break it regularly, and neither is specific to any one connector: - BCC. The BCC recipient is, for obvious reasons, not mentioned in the visible standard headers. Most provider mail servers keep the original recipient in a special, non-standard header field, and a connector that knows that field routes the message correctly. But under some circumstances (mail servers in between and their configuration) the BCC information is stripped completely before the message reaches the connector. Then no POP3 connector can distribute it ( knowledge base: BCC recipients do not receive the email ). - Mailing lists. Many list servers do not show the recipient address in the To: field, and the subscriber address can be removed on the way. If no header field carries a recipient in your domain, the message has no local recipient and goes to the postmaster ( knowledge base: mailing-list mail is not distributed correctly ). The practical test is to open the headers of one misrouted message (in Outlook: File › Properties, the Internet headers box) and look for a field that still names the intended recipient. If there is one, the connector can usually be told to read it; if there is none, the only fix is an individual mailbox for that user or that list. ### What happens to messages the connector cannot place With a catch-all mailbox the connector must also handle two situations that a single-user mailbox never sees. The first is a message addressed to several people, some outside your domain: the SMTP handover needs every recipient decoded, and Exchange would answer with a complaint to the postmaster, or an automatic reply to the sender, for every address it does not own. That is what the accepted recipient domains list is for: the connector hands Exchange only the recipients in domains you declare yours ( why the accepted domains matter ). A message with no recipient in any accepted domain at all goes to the postmaster with the log entry that it has no local recipients ( knowledge base article ). The second is a message for an address in your domain that does not exist in Exchange, for example a former employee or a typo. Exchange has no option to accept all mail for a domain, so it bounces such messages. A connector can instead re-route mail to unknown recipients to a mailbox of your choice, such as the postmaster or an administrator ( knowledge base article ). Which you prefer is a policy decision: a non-delivery report tells the sender at once, a re-route lets a person look at the message first. ### Recommendation - Individual mailboxes when the provider offers them at reasonable cost. Routing is exact, BCC and mailing lists work, and there is nothing to filter. The price is one account per user and a little more administration when users change. - Catch-all only with a provider that adds a delivery header. If the provider records the original recipient in a header such as X-Original-To, Delivered-To or X-RCPT-TO, a catch-all mailbox routes correctly for almost all mail and is far less work to maintain. Test it with a BCC message before you rely on it. - Mix the two where needed. A catch-all account for the domain plus single-user accounts for a mailing-list subscription, or for the one user whose mail keeps arriving without recipient headers, is a normal configuration. ### How POPcon handles each mailbox type In POPcon every POP3 or IMAP account has a mailbox type . A single-user mailbox delivers all mail retrieved from that account to one internal recipient, regardless of the addresses in the headers. A catch-all mailbox is examined message by message: POPcon does not only evaluate the To: and CC: fields, because these frequently do not contain the real recipient, but a longer list of header fields, among them X-Original-To, Delivered-To, X-RCPT-TO, X-Envelope-To and Received; the complete list is shown on the Advanced configuration page. POPcon PRO added X-FORWARDED-FOR to that list in version 4.6.2 ( version history ). For catch-all accounts you enter your domain, without the @ , in the Accepted recipient domains box; only recipients in those domains are forwarded to Exchange. A re-route address on the same page receives messages whose recipients cannot be resolved in Exchange, while the postmaster from the General tab receives messages that have no recipient in any accepted domain. If a message arrives in several copies because it was sent to several of your users, POPcon delivers it to all of them from the first copy and discards the later copies with the same message ID. One catch-all detail from the knowledge base: the catch-all address itself ( catchall@yourcompany.com ) tends to appear in the headers as well and is a valid address in your domain, so each message would also be delivered to that mailbox. The knowledge base describes the Advanced-page option that removes that address from the recipients found in the headers. If you are setting this up for the first time, the four steps, including the accepted domains and the receive connector on the Exchange side, are in the guide How to download POP3 and IMAP mailboxes into Exchange 2016, 2019 and SE ; the trial is on the POPcon download page . ### Frequently asked questions ### Why do BCC recipients not get their copy from a catch-all mailbox? A BCC recipient is, by design, not named in the visible To: or CC: headers. Whether a connector can still route the message depends on the provider: many mail servers record the original recipient in a non-standard header such as X-Original-To, Delivered-To or X-RCPT-TO, and POPcon reads those. If a server in between has stripped that information, no POP3 connector can determine the BCC recipient, and the only reliable fix is an individual mailbox for the affected user. ### Why does mail from a mailing list end up with the postmaster? Mailing-list servers usually put the list address in the To: field and often remove the subscriber address before the message reaches the provider mailbox. If none of the header fields contains a recipient in one of your accepted domains, POPcon forwards the message to the postmaster and logs that it has no local recipients. Check the headers of one such message for a preserved recipient field; if there is none, subscribe the list from its own POP3 or IMAP mailbox and configure that account as a single-user mailbox. ### What is the accepted recipient domains field for? A message to several people, for example your colleague and a contact at another company, carries every address in its headers. Exchange would reject or bounce the foreign ones. The accepted recipient domains list, entered without the @ sign, tells the connector which domains are yours, so only those recipients are handed to Exchange. It is only used for catch-all mailboxes; a single-user mailbox always delivers to the one recipient you configure. ### Can I mix both mailbox types in one installation? Yes. Each POP3 or IMAP account in POPcon has its own mailbox type. A typical setup uses a catch-all account for the company domain plus single-user accounts for a mailing-list subscription or for a user whose provider strips the recipient headers. The accounts are downloaded on the same schedule and delivered to Exchange through the same receive connector. More on inbound mail flow in the Exchange mail flow guides , or in the knowledge base . Auf Deutsch: Catch-all-Postfach oder ein POP3-Postfach pro Benutzer? . --- ## Download POP3 and IMAP mailboxes into Exchange 2016 to SE Source: https://www.servolutions.com/guides/download-pop3-imap-into-exchange Language: en Exchange mail flow guides › Inbound: POP3 and IMAP retrieval ### How to download POP3 and IMAP mailboxes into Exchange Server 2016, 2019 and SE To bring provider POP3 or IMAP mailboxes into an on-premises Exchange Server you run a connector service that logs in to each mailbox on a schedule, downloads the messages and submits them to Exchange over SMTP through a receive connector that allows relay from the connector’s IP. Exchange itself has no such connector (see Does Exchange Server have a built-in POP3 connector? ), so the work splits into two halves: a short preparation on the Exchange side and the account setup in the connector. This guide uses POPcon for the connector half. Updated on 2026-09-14 The Exchange steps follow our Exchange 2013 / 2016 configuration guide . Exchange 2016 and 2019 manage receive connectors in the same place, the Exchange admin center under Mail flow › Receive connectors , as described on Microsoft Learn under Receive connectors in Exchange Server ; POPcon supports Exchange Server SE as well ( requirements ). Not sure yet whether to collect the mail or to point the MX record at the server instead? POP3 retrieval or MX record to Exchange compares the two designs. ### What you need before you start | Item | Where | Why | | --- | --- | --- | | Your internet domain as an accepted domain | Exchange admin center › Mail flow › Accepted domains | Exchange rejects delivery for a domain it does not own with 550 5.7.1 Unable to relay | | Mailboxes that carry the provider addresses | E-mail address policy or the individual recipient | The connector hands each message to a recipient address; Exchange must know that address | | Provider server name, protocol and port | Your provider’s help pages | POP3 110, POP3-SSL 995, IMAP 143, IMAP-SSL 993 are the defaults | | Mailbox login, or OAuth 2.0 for Microsoft 365 and Gmail | Microsoft 365 walkthrough , Gmail walkthrough | These two providers are connected through a Microsoft or Google sign-in instead of a stored password — why, and what a service does with the token, is in Basic authentication is gone: Microsoft 365 by IMAP with OAuth2 | | A Windows machine for the connector | The Exchange server or any other Windows Server / Windows 7 to 11 machine ( where to install it ) | The service needs about 10 MB plus space for messages waiting to be forwarded | | TCP port 25 open from that machine to Exchange | Windows firewall and any firewall in between | The handover to Exchange is plain SMTP on port 25 | | A postmaster mailbox in Exchange | Any real mailbox, for example the administrator | Receives every message whose recipient cannot be resolved, and status notifications | ### Step 1: Add your internet domain to the accepted domains Open the Exchange admin center ( https:///ecp ), go to Mail flow and select Accepted domains . The default entry is usually the internal Active Directory domain; leave it and add a new one with the + icon. Enter a descriptive name, the internet domain the provider mailboxes belong to, and select Authoritative domain , which tells Exchange that this server holds every mailbox of that domain. Save. If you skip this step, every message the connector submits is refused with 550 5.7.1 Unable to relay , the single most common error in a fresh setup ( knowledge base article ). While you are in the admin center, make sure the users have SMTP addresses in that domain. The e-mail address policy under Mail flow › Email address policies assigns them in one format to all current and future users; the configuration guide shows the dialog, together with the send connector for outbound mail. ### Step 2: Let the receive connector accept mail from the connector POPcon delivers to Exchange over SMTP without authentication, so the receive connector that answers on port 25 has to accept anonymous connections from the connector’s IP address. Under Mail flow › Receive connectors select the Default Frontend connector and edit it: - General: raise Maximum receive message size from the default 10 MB to 100 MB, so larger messages do not get stuck between the connector and Exchange. You can limit sizes again later in the organisation settings or per mailbox, and Exchange will then return a non-delivery report for oversized mail. - Security: tick Anonymous users under permission groups. Without it Exchange answers 530 5.7.1 Client was not authenticated ( knowledge base article ). - Scoping: check that the remote IP ranges include the machine the connector will run on, and that the network adapter bindings show the server’s IP address or All available IPv4 on port 25. The FQDN field does not matter for POPcon. Two notes. First, do not install the Windows Simple Mail Transfer Protocol feature on the Exchange server: it would compete with the Exchange transport for port 25. Second, this is not an open relay: the anonymous permission lets the connector deliver to your own accepted domains only. A separate relay connector, as described in Microsoft’s Allow anonymous relay on Exchange servers , is only needed when a device or application must send to external recipients through Exchange, which a POP3 connector never does. ### Step 3: Install the connector and add the provider mailboxes Download POPcon , run the installer on the machine you chose and start POPcon Administrator. It installs the POPcon service that does the work in the background and the administrator program you configure it with. Click Configure and work through three tabs: - General: enter the postmaster address. Use a real mailbox inside Exchange; messages without a valid recipient are forwarded there, and a non-existent postmaster means they are lost. The log options can stay at their defaults. - POP3/IMAP: click Add for each provider mailbox. Choose the server type (POP3, POP3-SSL, IMAP or IMAP-SSL), enter the server name, user name and password, and the port if it differs from the default for that type (which protocol and port to take, and why the encryption setting must match the port: POP3 or IMAP for retrieving provider mailboxes into Exchange? ). Then decide the mailbox type: a single-user mailbox delivers everything to one Exchange recipient you name here, a catch-all mailbox receives mail for the whole domain and is split by the recipient headers (which to choose: catch-all vs one mailbox per user ). For catch-all accounts enter your domain, without the @ , in the Accepted recipient domains box; that is how POPcon tells local recipients from the rest ( why the accepted domains matter ). Finally choose whether downloaded mail is deleted at the provider, left there indefinitely, or left for a number of days. Microsoft 365 and Gmail accounts are connected with the OAuth2 button instead of a password; the walkthroughs are in the knowledge base ( Microsoft 365 , Gmail ). - Exchange: enter the Exchange server’s network name, for example MAILSERVER , not your internet domain. Everything else can stay at its default. The individual settings are described on the POP3/IMAP configuration page, the schedule on the scheduling page. ### Step 4: Test the first retrieval cycle Confirm the configuration with OK and click Trigger mail retrieval on the main screen. The scrolling log shows the login to the provider mailbox, each downloaded message and the SMTP handover to Exchange; the same text goes to POPconSrv.log in the POPcon program folder. A clean cycle ends with the messages in the Exchange mailboxes. Then set the schedule: the simple mode waits a fixed number of minutes between cycles, down to 1 minute, and 0 means continuous retrieval; the complex mode runs at exact times per weekday. From here on the service works without the administrator program being open. ### When it does not work Almost every failed first setup lands in one of these rows. The log line tells you which. | Symptom | Usual cause | Fix | | --- | --- | --- | | Messages download, nothing reaches Exchange | Wrong server name on the Exchange tab, transport service not running, port 25 blocked | Downloads fine but cannot reach Exchange : ping, telnet server 25 , services, firewall, receive connector | | “Could not reach Exchange SMTP server — check that IP port 25 is not blocked” | Firewall between the machines, or the connector’s IP is not in the receive connector’s remote IP ranges | knowledge base article ; step 2, Scoping | | 550 5.7.1 Unable to relay | The recipient domain is not an accepted domain | Step 1; knowledge base article ; guide 550 5.7.1 Unable to relay | | 530 5.7.1 Client was not authenticated | Anonymous users not ticked on the receive connector | Step 2; knowledge base article | | Every message goes to the postmaster: “no local recipients” | Accepted recipient domains missing or entered with an @ | knowledge base article ; step 3, POP3/IMAP tab | | Large messages never arrive | A message size limit in Exchange: the receive connector or the organization-wide limit | Step 2, General; the waiting messages are resent from the TOOLARGE folder once the limit is raised. All limits and their defaults: Messages over 10 MB are not arriving | ### Frequently asked questions ### Does the connector have to run on the Exchange server itself? No. POPcon runs as a Windows service on Windows Server 2012 to 2025 or Windows 7 to 11, either on the Exchange server or on any other machine in the network. From a separate machine it must reach Exchange on TCP port 25, and the receive connector’s remote IP range has to include that machine’s address; otherwise the log shows that the Exchange SMTP server could not be reached. ### POP3 or IMAP: which should I choose for the provider mailbox? Both deliver the same messages into Exchange. POPcon supports POP3, POP3-SSL, IMAP and IMAP-SSL with the default ports 110, 995, 143 and 993; take the protocol and port your provider documents and prefer the encrypted variant. For Microsoft 365 and Gmail mailboxes the OAuth 2.0 walkthroughs in the knowledge base use IMAP. If another client reads the same mailbox, set the account to leave messages on the server for a number of days. ### Can one provider mailbox for the whole domain serve every Exchange user? Yes. Configure it as a catch-all mailbox and enter your domain in the accepted recipient domains list. POPcon reads the To:, CC:, X-Envelope-To, Delivered-To and other header fields of each message and delivers it to the matching Exchange mailbox. Messages without a recipient in one of the accepted domains go to the postmaster, or to a re-route address you configure for the account. ### How often is mail collected? With simple scheduling POPcon waits a fixed number of minutes between retrieval cycles, minimum 1 minute; the value 0 starts the next cycle immediately after the previous one. Complex scheduling lets you set exact retrieval times per weekday instead, for example every 30 minutes during business hours only. The Trigger mail retrieval button in POPcon Administrator starts a cycle at once. More on inbound mail flow in the Exchange mail flow guides , or in the knowledge base . Auf Deutsch: POP3- und IMAP-Postfächer in Exchange Server 2016, 2019 und SE abholen . --- ## Exchange message size limits: mail over 10 MB not arriving Source: https://www.servolutions.com/guides/exchange-message-size-limit-pop3-connector Language: en Exchange mail flow guides › Authentication and SMTP errors ### Messages over 10 MB are not arriving: size limits between the POP3 connector and Exchange When large messages go missing between a provider mailbox and Exchange, the limit is almost always one of Exchange’s own message size limits — on the receive connector, in the organization-wide transport settings or on the mailbox — and not the connector. Exchange enforces the most restrictive of these limits. A POP3/IMAP connector such as POPcon has no practical size limit of its own; a message that Exchange refuses because of its size is kept in the connector’s TOOLARGE folder and can be delivered again once the limit has been raised. Updated on 2026-10-02 The Exchange behaviour on this page is taken from Microsoft Learn, where it is documented for Exchange Server 2016, 2019 and Subscription Edition; the connector side is taken from the POPcon knowledge base, whose articles on this subject were written for Exchange 2007 and 2010, and from our Exchange configuration guides. Where the two give different default values, both are named. ### Where Exchange limits the size of a message Microsoft’s reference is Message size and recipient limits in Exchange Server . It lists limits at four levels — organization, connector, server and mailbox — of which three matter for mail that a connector hands to Exchange over SMTP, plus the limit on the message header: | Limit | Default per Microsoft (2016, 2019, SE) | Exchange admin center | Exchange Management Shell | | --- | --- | --- | --- | | Organization: maximum size of a message received | 10 MB | Mail flow › Receive connectors › More options › Organization transport settings › Limits › Maximum receive message size (MB) | Set-TransportConfig , parameter MaxReceiveSize | | Organization: maximum size of a message sent | 10 MB | Same tab, Maximum send message size (MB) | Set-TransportConfig , parameter MaxSendSize | | Receive connector: maximum size of a message | 36 MB | Mail flow › Receive connectors › Edit › General › Maximum receive message size (MB) | Set-ReceiveConnector , parameter MaxMessageSize | | Receive connector: maximum size of all header fields | 256 KB | Not available | Set-ReceiveConnector , parameter MaxHeaderSize | | Recipient: maximum size of a message that can be sent to a mailbox | Unlimited | Recipients › Mailboxes › Edit › Mailbox features › Message size restrictions › Received messages | Set-Mailbox , parameter MaxReceiveSize | | Mail flow rule: message or attachment size | Not configured | Mail flow › Rules , condition on the message size or on the size of any attachment | Set-TransportRule , parameters MessageSizeOver , AttachmentSizeOver | Two details of the organizational limits are easy to miss, and both concern mail that arrives from outside. First, they apply to anonymous, unauthenticated senders — and that is how a connector delivers: POPcon submits to Exchange over standard unauthenticated SMTP, the same way an internet mail server would. Second, Microsoft states that for inbound messages from external senders Exchange applies the organizational maximum send message size, while the maximum receive size is applied to the internal recipient: “a message size must be within the message size limits for both the sender and the recipient.” Raising only one of the two organizational values can therefore leave the other one in the way. ### Where the 10 MB comes from The number turns up in three places, which is why it is the size at which this problem is usually noticed: - The organizational limits. Microsoft lists 10 MB as the default for both the maximum receive size and the maximum send size of the organization in Exchange 2016, 2019 and SE. - The receive connector on older versions. Our knowledge base article Exchange does not accept emails larger than 10 MB gives 10 MB (10240 KB) as the default maximum message size of a receive connector on Exchange 2007 and 2010, and the Exchange 2013 configuration guide has the same value changed to 100 MB when the connector is set up. For Exchange 2016 and later Microsoft’s table gives 36 MB. Do not rely on either figure for a server that has been in service for years — read the value (step 1 below). - The SBS POP3 Connector. For Windows SBS 2008 Microsoft documented that “the maximum message size that can be processed by SMTP is 10 MB” and that the POP3 Connector therefore does not attempt to retrieve larger messages; it logs an event that advises you to download or delete the message manually or to increase the size Exchange accepts ( archived SBS 2008 documentation ). More on that connector in The SBS POP3 Connector and what replaced it . The limit is also reached earlier than its name suggests. Microsoft: “Base64 encoding increases the size of the message by approximately 33%, so the value you specify should be approximately 33% larger than the actual message size you want enforced.” Its example is a limit of 64 MB, which gives a realistic maximum message size of approximately 48 MB. By the same ratio a 10 MB limit is reached by roughly 7.5 MB of attachments. ### Which limit wins, and where the message stops Microsoft’s rule is short: “The order of precedence for message size limits is the most restrictive limit is enforced. The only question is where that limit is enforced.” For mail delivered by a connector that second sentence decides what happens to the message, because there are two places where it can stop and they behave differently: | Where the message is refused | What happens | Who notices | Where the message is afterwards | | --- | --- | --- | --- | | At the receive connector, during the SMTP session | Exchange refuses the message while the connector is handing it over. POPcon moves it to its TOOLARGE subfolder ( knowledge base ) | Nobody, unless somebody looks into the folder or the log: the sender gets no notice, because POPcon cannot generate non-delivery reports itself | As a .msg file in TOOLARGE, ready to be delivered again | | After the receive connector accepted it: organizational limit or mailbox limit | Exchange has taken the message and then finds it too large. According to the knowledge base, Exchange then sends a non-delivery report to the sender automatically and the TOOLARGE folder is not used ( article ) | The sender, through the non-delivery report | Rejected by Exchange; the sender has to send it again after the limit was raised | With the defaults Microsoft lists for 2016 and later — 36 MB on the receive connector, 10 MB for the organization — a message between the two values passes the connector and is refused afterwards. Microsoft describes exactly this arrangement as a waste of resources for a server that receives from the internet (“it’s a waste of system resources for the Internet Receive connector to accept large messages that are eventually rejected because of a lower organizational limit”) and recommends the same limits everywhere or the more restrictive limit where messages enter the organization. Behind a POP3 connector there is a reason to keep it the other way round, described under If the sender should be told below. The mailbox limit has one more property that causes confusion. Limits between authenticated senders and recipients — typically internal ones — are exempt from the organizational size restrictions, so a mailbox can be allowed larger messages than the organization. “However, this exemption applies only to messages sent between authenticated senders and recipients.” In Microsoft’s example the organizational limit is 10 MB and the marketing department is configured for 50 MB: these users “will be able to exchange large messages with each other, but not with Internet senders and recipients”. Mail from a connector arrives anonymously and falls under the second half of that sentence. ### How to raise the limits and deliver the waiting messages - Read the limits that are in force. Microsoft gives one command per level. Organization: Get-TransportConfig | Format-List MaxReceiveSize,MaxSendSize,MaxRecipientEnvelopeLimit . Connectors: Get-ReceiveConnector | Format-Table Name,Max*Size,MaxRecipientsPerMessage . A mailbox: Get-Mailbox | Format-List MaxReceiveSize,MaxSendSize,RecipientLimits . The lowest value you find is the one that stops the mail. - Choose the new value. Allow for the encoding: about 33 percent above the largest message you want to accept. The configuration guides and the knowledge base use 100 MB (102400 KB) on the receive connector. - Raise the receive connector limit. In the Exchange admin center edit the receive connector that accepts the connector’s sessions and change Maximum receive message size on the General tab; the Exchange 2013 / 2016 configuration guide shows the dialog. In the shell the cmdlet is Set-ReceiveConnector with the parameter MaxMessageSize , for example Set-ReceiveConnector "Default Frontend " -MaxMessageSize 100MB ; the knowledge base gives set-receiveconnector "*default*" -maxmessagesize 100MB for Exchange 2007 and 2010, where the limit is on the General tab of the connector under Server Configuration › Hub Transport › Receive Connectors . If several receive connectors exist, make sure you change the one that answers — which receive connector is answering explains how Exchange picks it. - Raise the organizational limits. In the Exchange admin center: Mail flow › Receive connectors › More options › Organization transport settings › Limits . In the shell: Set-TransportConfig with MaxReceiveSize and MaxSendSize . Change both, for the reason given above. On Exchange 2007 and 2010 the setting is under Organization Configuration › Hub Transport › Global Settings › Transport Settings . - Check the mailbox if only one recipient is affected. The default is unlimited; a value that somebody set years ago shows up in the Get-Mailbox command from step 1 and is changed with Set-Mailbox , parameter MaxReceiveSize , or under Message size restrictions in the mailbox properties. - Deliver the waiting messages. Move the .msg files from POPcon’s TOOLARGE folder into the PICKUP subfolder. POPcon picks them up in the next retrieval cycle and attempts delivery again ( how to resend them ). Messages that were refused after Exchange had accepted them are not in that folder: their senders received a non-delivery report and have to send again. The knowledge base article Only messages under 10 MB come through has the screenshots of the three places for the older Exchange versions. ### If the sender should be told A message that waits in TOOLARGE is safe, but nobody outside knows that it did not arrive. If you would rather have oversized mail returned to the sender, the knowledge base describes the arrangement ( How to have NDRs sent for emails that are too large ): POPcon cannot generate non-delivery reports itself, so let Exchange do it. Set the receive connector limit high — the article uses 100 MB — so that the connector does not refuse the message at the wrong level, and set the organizational maximum receive size to the limit you actually want, for example 20 MB (and, following Microsoft’s note above, the maximum send size to the same value). Exchange then accepts the message from the connector, finds it larger than the organizational limit and sends the non-delivery report; the TOOLARGE folder is no longer used. This is the opposite of Microsoft’s general advice to reject as early as possible, and the difference is the delivery path. When a mail server on the internet delivers directly, an early refusal reaches the sending server, which informs its user. When a connector collects the mail from a provider mailbox, the sending server finished its work long ago; a refusal at the receive connector reaches only the connector. Which of the two you prefer — the message kept in TOOLARGE without notice, or a non-delivery report and no message — is a decision for your organization; the limits let you have either. The same choice for unknown recipients and out-of-office replies, and the way the report takes back to the sender, are in NDRs for external senders behind a POP3 connector . ### Symptoms and the limit behind them | Symptom | Limit behind it | Fix | | --- | --- | --- | | Large messages never arrive, the sender hears nothing, .msg files collect in TOOLARGE | Receive connector, MaxMessageSize | Steps 3 and 6 | | The sender receives a non-delivery report with status 5.3.4, “Message size exceeds fixed maximum message size” | A message size limit; Microsoft notes that this error “can be generated by the source or destination messaging system” ( DSNs and NDRs in Exchange Server ) | Step 1 to find the lowest value, then steps 3 and 4 | | The sender receives a non-delivery report with status 5.2.3, “RESOLVER.RST.RecipSizeLimit; message too large for this recipient” | The recipient’s own limit | Step 5 | | 552 5.3.4 Header size exceeds fixed maximum size , message in BADMAIL | Not the message size but the header size, MaxHeaderSize on the receive connector | Knowledge base article ; the row in the table of Exchange SMTP error codes | | On Windows SBS 2008 with the built-in POP3 Connector: the message stays in the provider mailbox and an event is logged | The connector’s 10 MB rule | Download or delete the message manually or raise the Exchange limit, as the event advises; comparison with a current connector | The reply Exchange gave to the connector is in the log, for POPcon the file POPconSrv.log in the program directory. The complete setup of the receive connector is in How to download POP3 and IMAP mailboxes into Exchange . ### Frequently asked questions ### Does the POP3 connector itself limit the size of a message? POPcon does not. Its knowledge base states that POPcon handles messages up to 100 MB and beyond and has no practical size limit of its own; when only messages under 10 MB come through, the restriction comes from Exchange. The SBS 2008 POP3 Connector was different: according to Microsoft it did not attempt to retrieve messages larger than 10 MB at all. ### What are the default message size limits in Exchange Server 2016, 2019 and SE? Microsoft lists 10 MB for the organizational maximum receive size and 10 MB for the organizational maximum send size, 36 MB for a receive connector, 10 MB for a send connector and no limit on a mailbox. The most restrictive limit is the one that is enforced. Our knowledge base and configuration guides, written for Exchange 2007 to 2013, give 10 MB (10240 KB) as the receive connector default, so read the values on your own server before changing anything. ### Why is an attachment smaller than the limit still rejected? Attachments travel Base64 encoded, and Microsoft puts the growth at approximately 33 percent: a limit must be set about 33 percent higher than the real message size you want to allow. Microsoft's example is a 64 MB limit that gives a realistic maximum message size of about 48 MB. By the same ratio a 10 MB limit is reached by roughly 7.5 MB of attachments. ### Are the messages in the TOOLARGE folder lost? No. POPcon moves a message that Exchange refused because of its size into the TOOLARGE subfolder as a .msg file and keeps it there. After the limit in Exchange has been raised, move the files from TOOLARGE into the PICKUP subfolder; POPcon picks them up in the next retrieval cycle and delivers them again. ### I raised the limit on one mailbox. Why is large mail from the internet still refused? Because the organizational limits still apply to it. Microsoft exempts messages between authenticated senders and recipients, typically internal ones, from the organizational size restrictions, so a higher mailbox limit works for internal mail. For messages from anonymous senders, which is how internet mail and mail delivered by a POP3 connector arrive, the organizational limits apply. Raise the organizational values as well. More in the Exchange mail flow guides , on the POPcon product page, the POPcon download page or in the knowledge base . Auf Deutsch: Nachrichten über 10 MB kommen nicht an . --- ## Multiple smart hosts in Exchange 2016/2019: two ways Source: https://www.servolutions.com/guides/exchange-multiple-smart-hosts Language: en Exchange mail flow guides › Outbound: send connectors and smart hosts ### Multiple smart hosts in Exchange 2016/2019: per recipient domain (built in) and per sender (with a relay) Exchange supports several smart hosts natively only by recipient domain: one send connector per destination address space, each with its own smart host and cost; routing by sender needs an additional relay hop. This guide shows both setups step by step, the commands to verify them, and a table to decide which one your situation calls for. Updated on 2026-09-17 ### First decide which “multiple” you mean “Several smart hosts” describes two different requirements, and only one of them is a checkbox in Exchange. - Different destinations, different smart hosts. Mail to a partner, a parent company or a particular country must leave through a dedicated gateway, everything else through the normal route. The decision depends on the recipient. Exchange does this with its own send connectors (method A). - Different senders, different smart hosts. Mail from company-a.example must leave through provider A with login A, mail from company-b.example through provider B with login B, because each provider relays only for its own customers’ addresses. The decision depends on the sender. Exchange has no setting for that; it takes one extra relay hop (method B). Why that is so is the subject of the companion guide Exchange send connectors route by recipient domain, not sender . ### How Exchange picks one of several send connectors Microsoft documents the selection in Connector selection in external message routing . For a message to an external recipient, Exchange first drops every connector whose message size limit is smaller than the message, then keeps only connectors that are enabled, visible from the local Active Directory site (unscoped, or scoped to this site) and configured with an address space that matches the recipient’s address. From that list the connector with the most specific address space wins. Microsoft’s example: for julia@marketing.contoso.com the order of preference is marketing.contoso.com , then *.contoso.com , then * . Only when two connectors match with the same specificity does the cost decide, lower being preferred, followed by the hop count and finally the connector name. The address space syntax is short ( Send connectors in Exchange Server ): * means all domains, contoso.com means that domain without its subdomains, *.contoso.com means the domain and all subdomains. In the Exchange Management Shell the full form is Type:AddressSpace;Cost , for example SMTP:*;1 ; the cost ranges from 1 to 100, and a lower cost is the better route ( New-SendConnector ). If no enabled, visible connector matches a recipient domain at all, the message waits in the Unreachable queue; the causes and the fix are in “A matching connector cannot be found to route the external recipient” . ### Method A: one smart host per recipient domain, with Exchange alone This follows Microsoft’s procedure Create a Send connector to route outbound mail through a smart host (Exchange 2016, 2019 and Subscription Edition). The archived article Configure a Dedicated Send Connector for a Specific Domain describes the same idea for Exchange 2010. - Keep the default route. You need one send connector with the address space * for all other external mail, either with DNS delivery or with your usual smart host. Most servers already have it. - Create the dedicated connector. In the Exchange admin center go to Mail flow > Send connectors > Add . Give it a descriptive name, choose the type Custom , select Route mail through smart hosts and add the smart host by IP address or FQDN. Choose the authentication the smart host requires; if it is a login, use Offer basic authentication only after starting TLS rather than plain Basic authentication, which sends the password in clear text. - Set the address space. Add the recipient domain as an SMTP address space, for example partner.example , or *.partner.example to include subdomains, with cost 1. Leave Scoped send connector unticked unless you deliberately want the connector to be visible only inside one Active Directory site. Select the source server and finish. - Repeat for every destination that needs its own smart host. Each dedicated connector must carry a different recipient domain. The same in the Exchange Management Shell, using Microsoft’s documented syntax: New-SendConnector -Name "Partner via gateway" -AddressSpaces "SMTP:partner.example;1" -Custom -DNSRoutingEnabled $false -SmartHosts gateway.partner.example -SmartHostAuthMechanism None New-SendConnector -Name "Smart host to Internet" -AddressSpaces * -Custom -DNSRoutingEnabled $false -SmartHosts 192.168.3.2 -SmartHostAuthMechanism None Verify what Exchange will choose from: Get-SendConnector | Format-List Name,Enabled,AddressSpaces,SmartHosts,Port,IsScopedConnector,SourceTransportServers Then send a message to the partner domain and one to any other domain. Microsoft’s own check is the same: send a test message, and turn on protocol logging for the send connector if you want to see the session. Because the more precise address space wins regardless of cost, the partner connector takes mail for partner.example even though the * connector has the same cost of 1. Two details that save time. A send connector may list several smart hosts, but they are alternatives for one route and share one authentication setting, so this is a redundancy feature, not a way to use two providers. And two connectors with the address space * do not split your mail; the one with the lower cost is preferred for all of it. ### Method B: one smart host per sender, with a relay behind a single connector When the smart host must depend on the sender, Exchange keeps exactly one send connector and hands everything to a local relay that knows the senders. MultiSendcon is that relay: a Windows service that accepts mail from Exchange on an alternative port (Exchange sees it as an ordinary smart host) and distributes it to the SMTP account that belongs to the sender. The full walk-through with screenshots is the MultiSendcon installation guide ; in short: - Install. Run the installer from the download page on the Exchange server. It starts the service and creates a send connector named MultiSendcon in Exchange with the address space * , port 2500 and a cost of 100, so all mail still takes your existing connectors until you are ready. If the installer cannot create the connector, one command does it ( knowledge base: create the MultiSendcon send connector manually ): new-sendconnector -name MultiSendcon -Addressspaces "SMTP:*;100" -port 2500 -SmarthostAuthMechanism none -smarthosts 127.0.0.1 - Master relay. In MultiSendcon Administrator, Configure > Master relay , select the local IP address the service listens on and leave the port at 2500. Limit the IP addresses that may connect, so the relay can never be used from outside. - One SMTP account per provider. On the Relay servers tab choose Add Relay Server for each smart host: server name, port (typically 25, 587 or 465; SSL is switched on automatically on 465), user name and password, and the sender address filter that decides who uses it, *@company-a.example for a whole domain or user@company-b.example for one address. A blank filter matches every sender. When several accounts match, the topmost entry wins, so put single addresses above their domain; two accounts with the same mask are tried in list order, which gives you a primary and a fallback relay. Add Direct DNS creates an entry that delivers straight to the recipient’s mail server by MX lookup, useful as a fallback for addresses that no relay account matches. - NDR handling. Enter the name or IP address of your Exchange server as the SMTP server, so non-delivery reports for mail a provider refuses find their way back to the sender or to a postmaster. - Test each account with the built-in SMTP account test . Use a From address that matches the account’s sender filter, and watch the Administrator log for the provider’s answer. - Switch Exchange over. On the MultiSendcon send connector change the address space cost from 100 to 1 (enable the connector if Exchange shows it as disabled) and replace the smart host 127.0.0.1 with the IP address you selected on the Master relay tab. In the shell that is Set-SendConnector MultiSendcon -AddressSpaces "SMTP:*;1" -SmartHosts . Send a message from each sender domain and follow it in the Administrator log to the right account. ### Method A and method B side by side | | A: per recipient domain (Exchange only) | B: per sender (Exchange + relay) | | --- | --- | --- | | What selects the smart host | The recipient’s domain, through the connector’s address space | The sender’s address or domain, through the account’s sender mask; optionally the recipient as well | | Send connectors in Exchange | One per destination plus the * connector | One ( * , port 2500, cost 1) | | Credentials | One authentication setting per connector | One login per SMTP account, as many accounts as you need | | Order of evaluation | Most specific address space, then cost, hop count, connector name | List order in the Relay servers tab; topmost match wins | | Fallback | A second connector with the same address space and a higher cost | A second account with the same sender mask below the first | | Where you test | Test message plus the send connector protocol log | Account test dialog plus the MultiSendcon Administrator log | | Extra software | None | One Windows service on the Exchange server | | Typical use | Partner gateway, outbound filtering appliance for some destinations | Several companies or domains on one server, each with its own provider relay | The two methods combine without conflict. A dedicated connector for partner.example keeps winning for that destination, because its address space is more specific than the * of the MultiSendcon connector; everything else goes to the relay and is sorted by sender there. ### Frequently asked questions ### Can two send connectors both have the address space *? Yes, Exchange accepts it, but it does not do what most administrators expect. Both connectors then match every external recipient with the same specificity, and Exchange picks the one with the lower address space cost. Microsoft describes the cost as a tool for mail flow optimization and fault tolerance when the same address space sits on several connectors: you get a preferred route and a second one behind it, for all mail. It does not split mail by sender domain, because the sender is not part of the selection. ### What happens if I put two smart hosts on one send connector? A send connector can list several smart hosts, by IP address or FQDN, and Exchange treats them as alternatives for the same route. They share the connector’s single authentication setting: Microsoft’s documentation for the dedicated-connector procedure notes that when you specify more than one smart host on a send connector, all of them must accept the same user name and password. Two providers with two different logins therefore cannot live on one connector; they need one connector each, or a relay that holds the credentials per provider. ### Do I need to disable my old send connector when I add the MultiSendcon connector? Not necessarily. The MultiSendcon installer creates its connector with the address space * and a cost of 100, so nothing changes until you lower the cost to 1. From then on it is preferred over an existing * connector with a higher cost, and the old connector stays in place as the route Exchange falls back to. Only enabled connectors take part in routing, so if you want to be certain that no mail bypasses the relay, disable the old connector once your tests are clean. Connectors with a more specific address space, such as a partner domain, still win over * and keep working as before. ### Does this work on Exchange 2013, Exchange 2010 or SBS 2011? The native method is one send connector per destination address space. Microsoft’s current procedure is written for Exchange 2016, 2019 and Subscription Edition and uses the Exchange admin center; the archived Exchange 2010 article describes the same steps in the Exchange Management Console. For routing per sender, the MultiSendcon system requirements list Exchange Server 2019, 2016, 2013, 2010, 2007, 2003 and 2000 including all Small Business Server editions, and the product page additionally names Exchange Server SE. More on outbound mail flow in the Exchange mail flow guides , or in the knowledge base . Auf Deutsch: Mehrere Smarthosts in Exchange 2016/2019 . --- ## Exchange: 'A matching connector cannot be found' - fix Source: https://www.servolutions.com/guides/exchange-no-matching-send-connector Language: en Exchange mail flow guides › Outbound: send connectors and smart hosts ### Exchange: “A matching connector cannot be found to route the external recipient” — causes and fix Exchange Server puts a message into the Unreachable queue with the last error “A matching connector cannot be found to route the external recipient” when no enabled send connector that is visible from the sending server’s Active Directory site has an address space covering the recipient’s domain. The usual causes are a connector without the address space * , a disabled connector, a scoped connector in another site, or an address space that does not match the way you expected. Nothing is wrong with the message or the recipient; the routing table simply has no exit for that domain. Updated on 2026-09-19 ### What the error means For every external recipient Exchange has to pick one send connector. Microsoft documents the procedure in Connector selection in external message routing (applies to Exchange 2016, 2019 and Subscription Edition). Exchange first removes connectors whose message size limit is smaller than the message, then keeps only the connectors that meet all three of these conditions: - the connector is enabled, - the connector is not scoped, or it is scoped to the local Active Directory site, - the connector has an address space that matches the recipient’s e-mail address. If that list is empty, Microsoft’s wording is: “If there is no matching connector for an SMTP address space, the recipient is marked as unreachable and the message is routed to the Unreachable queue.” The message stays there; the sender gets no bounce at this point. The queues documentation describes the Unreachable queue as the place for messages that cannot be routed to their destinations and adds that this is typically caused by configuration changes that modified the routing path. That matches practice: the error almost always appears right after somebody created, deleted, disabled or re-scoped a send connector. ### The causes, and how to recognise each | Cause | How it shows | Fix | | --- | --- | --- | | No connector with the address space * | Mail to a few domains leaves, everything else is stuck. The connectors list only specific domains. | Add one connector with the address space * for all other Internet mail, or add * to an existing connector. The more specific connectors still win for their domains. | | The connector is disabled | Enabled is False . Only enabled connectors are used in routing decisions, so a disabled connector is the same as none. | Set-SendConnector "Name" -Enabled $true , or enable the connector in the EAC under Mail flow → Send connectors. | | A scoped connector in another Active Directory site | IsScopedConnector is True and the source servers are in a different site from the server that holds the message. A scoped connector is invisible to Exchange servers in other sites and is not used in their routing decisions. | Remove the scope (EAC: the Scoping tab of the connector; shell: -IsScopedConnector $false ) or create a connector that the affected site can see. | | The address space does not match the recipient domain | contoso.com covers that domain without subdomains, so mail to user@mail.contoso.com has no match; only *.contoso.com covers the domain and all subdomains. The documented forms are * , a domain, and *. domain. An address space is a destination domain, not an e-mail address. | Correct the address space to one of the three documented forms. | | No usable source server | Microsoft requires at least one Mailbox server or Edge Transport server to host the connector. After a migration the only source server listed may be one that has been removed. | Add a current Mailbox server on the connector’s Scoping tab, or with -SourceTransportServers . | The syntax and the scoping rule are in Send connectors in Exchange Server . Two things that look like candidates are not: a message size limit on the connector leads to a non-delivery report when the message is too large for every connector, not to this error; and the cost value only decides between connectors that already match, so a high cost never makes a connector unavailable. ### Check it in the Exchange Management Shell One command shows every setting that takes part in the decision ( Get-SendConnector ): Get-SendConnector | Format-List Name,Enabled,AddressSpaces,IsScopedConnector,SourceTransportServers,MaxMessageSize Read the output against the recipient domain of a stuck message. Is there an enabled connector whose AddressSpaces contains * or the recipient’s domain? Is it unscoped, or are its source servers in the same site as the server where the message waits? Then look at the queue itself: Get-Queue -Identity Mailbox01\Unreachable | Format-List Identity,Status,MessageCount,LastError Get-Message -Queue Mailbox01\Unreachable | Format-Table FromAddress,Subject,LastError Replace Mailbox01 with your server name. The recipient domains of the waiting messages tell you which address space is missing. If all external mail is stuck, look for the * connector; if one domain is stuck, look for a connector that claims that domain and is disabled, scoped elsewhere or written without the subdomain wildcard. ### When a second connector interferes The most confusing case is a connector that should not be involved at all. Exchange prefers the most specific address space : for julia@marketing.contoso.com Microsoft gives the order marketing.contoso.com , then *.contoso.com , then * . But a connector only takes part in that comparison if it passed the three conditions above. A specific connector that is disabled or scoped to another site therefore does not win and then fail; it is simply ignored, and the mail falls through to the * connector if one exists. If no * connector exists, the domain is unreachable. The reverse also happens: an old test connector with a specific address space that is enabled takes the mail for that domain away from your main connector and sends it to a smart host that no longer accepts it. That produces a delivery queue in Retry, not the Unreachable queue, and it is worth telling the two apart before changing anything. When you are not sure which connector Exchange uses, disable the suspects one at a time and watch which queue the next test message enters. ### After the fix: getting the waiting mail out Exchange resubmits the Unreachable queue to the categorizer by itself when it detects a configuration update, unless the queue has been suspended. If the messages are still waiting a few minutes after your change, resubmit them. Microsoft’s queue procedures state that Queue Viewer cannot resubmit a queue and give this command for exactly this case: Retry-Queue -Identity Mailbox01\Unreachable -Resubmit $true Resubmitting sends the messages back to the Submission queue, so the categorizer makes a fresh routing decision with the corrected connectors. Messages with the status Suspended are not resubmitted; resume them first. ### The same error with a relay such as MultiSendcon Setups that route outbound mail by sender through a local relay reduce Exchange to a single send connector, which makes this error easy to cause and easy to fix. MultiSendcon receives all outgoing mail from Exchange on 127.0.0.1 , port 2500, through one connector with the address space SMTP:* , and chooses the provider relay per sender itself. The installer creates that connector disabled and with cost 100 , so that mail keeps leaving through the existing connector while you enter the relay accounts ( installation guide ). Two mistakes lead straight to the Unreachable queue: - The old connector is deleted or disabled before the MultiSendcon connector has been enabled. No enabled connector is left, and every external recipient is unreachable. Enable the connector and set the cost to 1. - The connector was never created, for example because PowerShell remoting was switched off during setup. Create it by hand with the command from the knowledge base article How to manually create the MultiSendcon send connector , then set the cost to 1. A cost of 100 on its own does not cause the error: as long as the connector is enabled and is the only one with * , Exchange uses it. The cost matters when an older * connector is still enabled beside it; then the lower cost wins, which is why the guide tells you to change 100 to 1. How several connectors and several smart hosts work together is described in Multiple smart hosts in Exchange 2016/2019 , and why Exchange cannot choose a connector by sender in Exchange send connectors route by recipient domain, not sender . MultiSendcon can be tried for 30 days from the download page . ### Frequently asked questions ### Do I have to resend the messages after I fix the send connector? Normally not. According to Microsoft Learn, messages in the Unreachable queue are resubmitted to the categorizer automatically when Exchange detects a configuration update, unless an administrator has suspended the queue. If the messages are still there after the change, resubmit the queue in the Exchange Management Shell with Retry-Queue -Identity \Unreachable -Resubmit $true. Queue Viewer cannot resubmit a queue; Microsoft documents this as a shell-only operation. ### Can a message size limit on the send connector cause this error? Not this one. A send connector whose maximum message size is smaller than the message is removed from the selection, but Microsoft documents a different outcome for that case: if the message exceeds the size restriction of all connectors, a non-delivery report is returned to the sender. The Unreachable queue and the missing-connector error are the outcome when no enabled, visible connector has an address space that matches the recipient. ### Why does only mail to one domain get stuck while everything else leaves? Then a connector without the address space * is doing the work. Exchange only considers connectors whose address space matches the recipient domain. If your connectors list individual domains, for example partner.example and *.contoso.com, every other destination has no connector at all. The usual repair is one connector with the address space * for all remaining Internet mail, next to the specific ones; the most specific match still wins for the listed domains. ### I use MultiSendcon. Which send connector must exist? One send connector with the address space SMTP:* that delivers to the smart host 127.0.0.1 on port 2500. The MultiSendcon installer creates it disabled and with cost 100, so that mail keeps flowing through your old connector while you set up the relay accounts. If you remove or disable the old connector before you have enabled the MultiSendcon connector, no enabled connector matches any external domain, and every outgoing message lands in the Unreachable queue with this error. Enable the connector and set its cost to 1. More on outbound mail flow in the Exchange mail flow guides , or in the knowledge base . Auf Deutsch: Exchange: „A matching connector cannot be found“ – Ursachen und Lösung . --- ## Does Exchange Server have a built-in POP3 connector? Source: https://www.servolutions.com/guides/exchange-pop3-connector-built-in Language: en Exchange mail flow guides › Inbound: POP3 and IMAP retrieval ### Does Exchange Server have a built-in POP3 connector? No. Exchange Server 2013, 2016, 2019 and Exchange Server SE include a POP3 service that lets clients read Exchange mailboxes over POP3, but no connector that fetches mail from external POP3 or IMAP mailboxes into Exchange. That function existed only in Windows Small Business Server, whose 2008 and 2011 editions shipped a POP3 Connector in the SBS console; the last version to include it was SBS 2011. On a standalone Exchange server the job is done by a separate connector service that downloads the provider mailboxes and hands the messages to Exchange over SMTP. Updated on 2026-09-12 ### Two different things are called “POP3” in Exchange The confusion comes from one word covering two opposite directions of mail flow. When an administrator searches for “Exchange POP3”, Microsoft Learn answers with the POP3 service. When the same administrator asks “how do I get the mail from our provider mailboxes into Exchange”, the answer is a connector, and Exchange does not have one. | | Exchange POP3 / IMAP4 service | POP3 connector | | --- | --- | --- | | Direction | Out of Exchange: a client reads an Exchange mailbox | Into Exchange: provider mailboxes are downloaded and delivered to Exchange users | | Who connects to whom | Outlook, a phone or another mail program connects to the Exchange server on port 110 or 995 | The connector connects to the provider’s POP3 or IMAP server, then submits to Exchange over SMTP | | Where it is configured | Exchange services Microsoft Exchange POP3 and POP3 Backend , external FQDN, port and TLS settings; disabled by default | Its own console: one entry per provider mailbox with server, login, protocol, schedule and the Exchange recipient(s) | | Included in Exchange 2013, 2016, 2019, SE | Yes | No | | Included in Windows SBS 2008 / 2011 | Yes (Exchange 2007 / 2010 inside SBS) | Yes, the SBS POP3 Connector | ### What the Exchange POP3 service actually does Microsoft describes POP3 and IMAP4 in Exchange Server as client-access protocols: users normally reach their mailboxes with Outlook (MAPI), Outlook on the web or Exchange ActiveSync, and POP3/IMAP4 are kept for clients that still rely on them. The services are not started by default. To use them you start Microsoft Exchange POP3 and Microsoft Exchange POP3 Backend , set them to automatic, configure the external server name, port and encryption method, and restart the services (see Microsoft Learn: POP3 and IMAP4 in Exchange Server and Enable and configure POP3 on an Exchange server ). Exchange listens on port 995 for TLS-encrypted connections and on port 110 for unencrypted or STARTTLS connections. Microsoft also notes that POP3 and IMAP4 functionality in Exchange 2016 and 2019 is basically unchanged from Exchange 2013. Nothing in that feature reaches out to another server. Enabling the POP3 service on Exchange therefore does not help with mail that sits in a mailbox at your Internet provider; it only lets a POP3 client pull mail out of Exchange. ### Where the “built-in connector” memory comes from: Small Business Server Windows Small Business Server bundled Exchange with a component that standalone Exchange never had. Microsoft’s documentation for the Windows SBS 2008 POP3 Connector describes it precisely: it retrieves e-mail from an external POP3 mailbox account and delivers it to the Exchange mailbox of a specified SBS user or distribution group, it can connect over SSL, it supports Basic, SPA and APOP authentication, and it has a Scheduling tab for the retrieval interval. Many small companies ran their whole inbound mail this way for a decade: the domain stayed at the provider, one POP3 mailbox per user or one catch-all mailbox for the domain, and the SBS connector emptied them into Exchange. When those companies moved from SBS 2011 to Exchange 2013, 2016 or 2019 on a regular Windows Server, the POP3 Connector did not come along (what it did and how a current connector compares: The SBS 2008/2011 POP3 Connector and its replacement ). It was an SBS console feature, not an Exchange feature, so a migrated Exchange organisation ends up with the POP3 service described above and no way to collect provider mailboxes. That is the moment the question in this guide’s title gets typed into a search box. ### What you use instead on Exchange 2013 to SE The replacement is a POP3/IMAP connector that runs as a Windows service next to (or on) the Exchange server. POPcon is a Windows service that downloads mail from POP3 and IMAP mailboxes into Microsoft Exchange Server and distributes it to the right mailboxes. It works the way the SBS connector worked, with the parts SBS shops usually missed: - Standard SMTP delivery. POPcon submits each message to Exchange over SMTP through a receive connector, exactly as any other SMTP sender would. It does not use Exchange-specific APIs, which is why one connector covers Exchange 5.5 through 2019 and Exchange Server SE, all SBS versions, and other SMTP servers such as Lotus Domino/Notes and Tobit David (see which Exchange versions POPcon works with and the system requirements ). - Catch-all mailboxes as well as one mailbox per user. For a single domain mailbox POPcon reads the To:, CC:, X-Envelope-To, Delivered-To and related headers to find the real recipient and delivers each message to that Exchange mailbox, with catch-all rules for anything that does not match. - POP3 and IMAP, with or without TLS, and OAuth 2.0 (modern authentication) for Microsoft 365 and Gmail mailboxes, so the connector keeps working after providers switch off password-only logins. - Any number of provider accounts from one installation, each with its own protocol, credentials, retrieval interval and distribution rules. - Runs on Windows Server 2012 to 2025 and Windows 7 to 11, on the Exchange server itself or on a separate machine. On the Exchange side the only preparation is a receive connector that accepts SMTP connections from the connector’s IP address; the complete setup from accepted domain to first test is in How to download POP3 and IMAP mailboxes into Exchange 2016, 2019 and SE , the Exchange dialogs in Configuring Exchange 2013 / 2016 to receive mail from POPcon , with older guides for Exchange 2010 and SBS 2011 and Exchange 2007 and SBS 2008 . What an upgrade to Exchange Server SE changes for such a connector, and what it does not, is in Exchange Server SE and POP3/IMAP mailbox retrieval . Read more about POPcon or download the free trial and point it at one provider mailbox to see the flow end to end. ### When you do not need a connector A POP3 connector solves one specific situation: mail for your users arrives in mailboxes at a provider, and Exchange has to go and get it. If your domain’s MX record points at your Exchange server, at a mail gateway in front of it, or at a hosted filtering service that relays to Exchange, inbound mail is already delivered by SMTP and a connector adds nothing. Companies usually keep collecting by POP3 for a transition period (the old provider mailboxes still receive mail for a while, or some addresses cannot be moved yet) and then switch the MX record once every address lives on Exchange. Both setups can run at the same time on the same server: SMTP for the domains whose MX points at Exchange, the connector for the mailboxes that remain at the provider. The guide POP3 retrieval or MX record to Exchange compares the two designs in detail. ### Frequently asked questions ### Is the Exchange POP3 service the same thing as a POP3 connector? No. The POP3 service lets a mail client such as Outlook or a phone read an Exchange mailbox over POP3; mail flows out of Exchange to the client. A POP3 connector logs in to an external POP3 or IMAP mailbox at your provider, downloads the messages and delivers them into Exchange; mail flows into Exchange. Exchange Server includes the first and has never included the second. ### Did Exchange 2013 or Exchange 2016 have a POP3 connector? No. Microsoft documents POP3 and IMAP4 in Exchange 2013, 2016, 2019 and Exchange Server SE as client-access protocols only. The POP3 Connector was a component of Windows Small Business Server, not of Exchange Server, and it was never offered for the standalone Exchange editions. ### Can I keep using the SBS POP3 Connector after migrating to a newer Exchange? No. The POP3 Connector is part of the Small Business Server console and runs only on the SBS machine. Once the SBS server is retired, the function has to be provided by a separate connector service that runs as a Windows service and submits the downloaded mail to the new Exchange server over SMTP. ### Do I need a POP3 connector at all if my MX record already points at Exchange? No. If the MX record for your domain points at your Exchange server (or at a gateway in front of it), inbound mail is delivered by SMTP and there is nothing to collect. A POP3 connector is only needed for mail that lands in provider mailboxes first: an ISP mailbox, a domain hosted at IONOS, Strato or GMX, a Gmail or Microsoft 365 mailbox, or addresses you cannot yet move to your own MX record. More on inbound mail flow in the Exchange mail flow guides , or in the knowledge base . Auf Deutsch: Hat Exchange Server einen eingebauten POP3-Connector? --- ## Exchange send connectors: route outbound mail by sender Source: https://www.servolutions.com/guides/exchange-send-connector-by-sender Language: en Exchange mail flow guides › Outbound: send connectors and smart hosts ### Exchange send connectors route by recipient domain, not sender — how to route outbound mail by sender address anyway An Exchange Server send connector is selected by the recipient’s domain (its address space) and cost, never by who sent the message; to send different sender domains through different smart hosts on-premises you need either separate Active Directory sites with scoped connectors, a transport agent, or an SMTP relay in front of Exchange that routes by sender. This guide explains how connector selection works, why the obvious workarounds fail, and what the three real options cost you in complexity. Updated on 2026-09-16 ### The question, and the short answer The setup is common: one Exchange Server hosts company-a.com and company-b.com , or a corporate domain plus a few addresses at a hosted provider. Each domain has its own provider relay with its own login, and each provider only accepts mail from the addresses that belong to that login. So the administrator creates two send connectors, one per smart host, and expects Exchange to use the right one for each sender. It does not, and no setting on the connector changes that. Microsoft’s own documentation lists what a send connector is selected by, and the sender is not on the list. ### How Exchange chooses a send connector According to Microsoft Learn, the send connector used to route a message to a recipient is selected during the routing resolution phase of message categorization, and the settings that matter are these ( Send connectors in Exchange Server , Mail routing in Exchange Server ): | Setting | What it does | Depends on the sender? | | --- | --- | --- | | Address spaces | The destination domains the connector is responsible for, for example * for every domain or *.contoso.com . A message is matched to the connector with the most specific address space for its recipient. | No | | Cost | Breaks ties between connectors with the same address space: the connector with the lower cost value is preferred. | No | | Scope | A scoped connector is visible only to Exchange servers in its own Active Directory site; unscoped connectors are visible to the whole forest. | No (depends on the sending server’s site) | | Source servers | Which Exchange servers may deliver through the connector. | No | | Network settings | DNS delivery or one or more smart hosts, plus the authentication for the smart host. | No | | Message size limit | Connectors whose limit is smaller than the message are skipped. | No | Every input to the decision describes the destination, the topology or the message size. The sender address, the sender’s domain, the mailbox database or the department are not evaluated. That is not an oversight in a particular version: the logic is, in Microsoft’s words, basically unchanged since Exchange 2010, and it applies to Exchange 2013, 2016, 2019 and Exchange Server SE alike. ### Why the obvious attempts fail - Two connectors with the address space * and different smart hosts. Both claim every destination. Exchange resolves the tie with the cost value, and nothing in the tie-break looks at the sender. Mail from every sender goes to whichever connector wins, or to both, and the provider that expects only its own domains answers with a sender or authentication error such as 530 SMTP authentication is required or a rejection of the sender address. - An address space per sender domain. The address space is the recipient domain. An entry company-b.com makes the connector responsible for mail to company-b.com, which is your own accepted domain and is delivered internally anyway. There is no field for the sending domain. - A mail flow (transport) rule. Rules can redirect, modify, copy or reject a message and can add recipients, but they run in a different stage and cannot name a connector or a smart host. This is exactly what the Exchange Online outbound connector can do with its rule condition, and what the on-premises product cannot. - A second Exchange server per domain. Only helps if the servers are in different Active Directory sites (see the first option below); two servers in one site share the same routing decision. ### The three ways that actually work | Option | How it works | What it costs you | | --- | --- | --- | | Separate Active Directory sites with scoped connectors | Each sender domain gets its own AD site with its own Exchange server and a scoped send connector for that provider. Because a scoped connector is only visible inside its site, mail submitted on that server can only leave through it. | One Exchange server and mailbox database per domain, AD site links to maintain, and users of a domain must live on that server. Supported by Microsoft, but heavy for the two-domains case. | | Custom transport agent | A routing agent written against the Exchange transport SDK inspects the sender and overrides the routing destination before categorization ends. | Code you write and maintain yourself, re-tested after every Cumulative Update, and running inside the transport pipeline where a bug stops all mail. | | Sender-routing relay in front of Exchange | Exchange keeps one send connector, which forwards everything to a local relay service. The relay matches the sender address against its rules and delivers through the provider relay with the credentials that belong to that sender. | One service to install and configure. Exchange itself stays unmodified; the routing rules live in the relay, and the Exchange queue viewer still shows the mail leaving. | The first two options are Microsoft mechanisms and are described on the Microsoft Learn pages linked above. The third is what MultiSendcon implements: it installs as a Windows service on the Exchange server, listens as a local smart host (by default on port 2500, because Exchange itself uses port 25 for its receive connectors), and the installer creates the send connector that points Exchange at it. If the installer cannot create the connector, for example because PowerShell remoting is disabled, one command in the Exchange Management Shell does it ( knowledge base: create the MultiSendcon send connector manually ): new-sendconnector -name MultiSendcon -Addressspaces "SMTP:*;100" -port 2500 -SmarthostAuthMechanism none -smarthosts 127.0.0.1 The address space * with cost 100 makes it the connector for all Internet mail; change the cost to 1 so it wins over any older connector. From then on Exchange makes exactly one routing decision, and the sender-dependent part happens in the relay. ### What the relay decides per sender Inside MultiSendcon each provider relay is an SMTP account with a sender mask: *@company-a.com for a whole domain, user@company-b.com for a single address, or a wildcard pattern. Each account carries its own relay server, port (25, 587 or 465), login and TLS settings, and optionally a recipient filter and a local IP address to send from. The first matching rule in list order wins, so a specific address can sit above its domain rule, and two accounts with the same mask form a primary/fallback pair. Senders that match no rule fall through to the Master Relay configuration, or can be handed back to Exchange’s own send connectors. A fixed-sender option replaces the outgoing address where a provider only accepts the authenticated account’s address, and it also fills in the empty envelope sender that Exchange uses for non-delivery reports and out-of-office replies, which some providers now reject ( knowledge base: IONOS blocks NDRs and out-of-office messages ). The same mechanism covers the related cases: several companies on one server, a corporate domain mixed with Google Workspace addresses, bulk mail on a separate IP for reputation reasons, or a destination that needs its own relay (recipient-dependent routing). Exchange 2003 through 2019 and Exchange Server SE are supported; the connector framework is the standard send connector, no transport agent or pipeline plug-in is installed. ### Exchange Online is different If your mailboxes are in Exchange Online, you do not need any of this: an outbound connector there can be set to be used only when a transport rule redirects messages to it , and the rule can match on the sender, so “route mail from these senders through this smart host” is a native configuration ( Conditional mail routing in Exchange Online ). This guide is about Exchange Server on-premises, where that option does not exist. ### Next steps - Step by step: Multiple smart hosts in Exchange 2016/2019 shows the native setup per recipient domain and the relay setup per sender side by side. - Two domains, two providers: install the MultiSendcon 30-day trial , let the installer create the send connector, add one SMTP account per provider with its sender mask, and send a test from each domain. - Only one provider but several logins: the same setup with one account per login. - The whole picture for two companies on one server, inbound and outbound: Hosting several companies or domains on one Exchange Server . - One provider, one login, but the empty-sender rejections: the lower-priced LITE edition replaces the empty sender and is enough for that case. The provider rules behind those rejections are in IONOS, Strato or GMX as the smart host for Exchange . ### Frequently asked questions ### Can a transport rule set the smart host in Exchange 2019? No. A mail flow rule on Exchange Server can modify, redirect or reject a message and can change its recipients, but it cannot choose a send connector or a smart host. Connector selection happens in the routing resolution phase of categorization, based on the address spaces, cost and scope of the send connectors. In Exchange Online the situation is different: an outbound connector there can be used only when a mail flow rule redirects messages to it, which is why the same question has a native answer in the cloud and none on-premises. ### Why does a second send connector with the address space * not route by sender? Both connectors advertise the same destination, every domain, and Exchange resolves the tie with the cost value; whatever breaks a tie between equal costs looks at the connectors and the topology, never at the sender. The sender address is not an input to that decision. You will see mail from every sender spread across both smart hosts, and the provider that expects only its own domains will reject the rest with an authentication or sender error. ### Can I run an open-source mail server in front of Exchange instead? Yes, any SMTP relay that supports sender-dependent transport and authentication can be placed between Exchange and the providers; Exchange only needs one send connector pointing at it. The trade-off is a second mail system with its own operating system, patching, certificates, queues and logs. The connector-service approach does the same routing as a Windows service on the Exchange server itself and keeps the Exchange queue viewer as the single place to look. ### Why does IONOS reject mail from my other domains? Providers such as IONOS accept mail through their authenticated SMTP relay only for sender addresses that belong to the login, and since 2024 IONOS also blocks messages with an empty envelope sender, which is how Exchange sends non-delivery reports and out-of-office replies. Routing each domain through the relay account it belongs to solves the first problem; replacing the empty sender with a fixed address solves the second. Both are described on the MultiSendcon pages and in the knowledge base. More on outbound mail flow in the Exchange mail flow guides , or in the knowledge base . Auf Deutsch: Exchange-Sendeconnectoren routen nach Empfängerdomäne, nicht nach Absender . --- ## Exchange Server SE and POP3/IMAP retrieval: what changes Source: https://www.servolutions.com/guides/exchange-server-se-pop3-imap-retrieval Language: en Exchange mail flow guides › Inbound: POP3 and IMAP retrieval into Exchange ### Exchange Server SE (Subscription Edition) and POP3/IMAP mailbox retrieval: what changes, what does not Exchange Server SE keeps the Exchange 2019 mail-flow model — receive connectors, send connectors, accepted domains — so a POP3/IMAP connector that submits its mail over SMTP works as it did before, and nothing in SE adds a built-in POP3 connector. Microsoft describes the first release, Exchange SE RTM, as “code equivalent to Exchange Server 2019 CU15” with three exceptions: the licence agreement, the product name and the build number. What does change for a shop that collects provider mailboxes is the route to SE: an in-place upgrade exists only from Exchange 2019 CU14 or CU15, every older version means a new server, and a new server means a new receive connector for the connector to deliver to. This guide lists what Microsoft states about SE, what that means for the connector, and what to check on each upgrade path. Updated on 2026-10-01 ### What Exchange Server SE is Exchange Server Subscription Edition (SE) is the on-premises Exchange version that follows Exchange Server 2019. Microsoft’s lifecycle page lists it under the Modern Lifecycle Policy with a start date of July 1, 2025; the Exchange Server supportability matrix states that “Exchange Server 2016 and Exchange Server 2019 have reached end of support on October 14, 2025”. The page What’s new in Exchange Server SE says about the first release: - “Exchange Server Subscription Edition (SE) Release to Manufacturing (RTM) is code equivalent to Exchange Server 2019 CU15, except for the following changes”: the licence agreement, the product name, and the build number. - “New features are introduced starting with the Exchange Server SE Cumulative Update (CU) 1.” - “You can perform an in-place upgrade from Exchange Server 2019 CU14 or CU15 directly to Exchange Server Subscription Edition (SE).” The companion page What’s discontinued in Exchange Server repeats the code-equivalence sentence for the step from 2019 to SE and names one removed feature for those coming from Exchange 2016 or 2013, Unified Messaging. Neither page lists a change to receive connectors, send connectors or accepted domains. ### What changes and what does not, for a shop that collects POP3/IMAP mailboxes | Topic | What Microsoft states for Exchange SE | What it means for the connector | | --- | --- | --- | | Fetching from external POP3/IMAP mailboxes | POP3 and IMAP4 exist as client access protocols: “to support clients that still rely on these protocols, you need to start the services” ( POP3 and IMAP4 in Exchange Server , applies to 2016, 2019 and SE) | No change: Exchange still does not retrieve mail from provider mailboxes. A separate connector service does that. | | Receive connectors | The same documentation page covers 2016, 2019 and SE. The default connector Default Frontend “accepts anonymous connections from external SMTP servers” ( Receive connectors in Exchange Server ) | No change in how the connector delivers: SMTP to port 25, Anonymous users permission group on the receive connector, as in the Exchange configuration guide . | | Where a receive connector lives | “A Receive connector is associated with the Mailbox server or Edge Transport server where it’s created” and is stored in Active Directory as a child object of that server | In-place upgrade: same server, same connector. New server: its own receive connectors, so the permission has to be set there again. | | Accepted domains | “Accepted domains are a global setting for the Exchange organization” ( Accepted domains in Exchange Server ) | They are already there when a new server joins the organization. Verify, do not re-create. | | Send connectors | A send connector has source servers , “the Exchange servers where the Send connector is hosted” ( Send connectors in Exchange Server ) | Matters for outbound relays such as MultiSendcon when the server changes: see below. | | TLS defaults | “TLS 1.2 and TLS 1.3 are the only versions which are enabled by default”; “TLS 1.3 is not yet supported for the Simple Mail Transfer Protocol (SMTP)” (What’s new, section for upgrades from Exchange 2016) | Only relevant if Allow StartTLS is switched on in the connector’s Exchange settings. POPcon lists TLS 1.2 / 1.3 encryption; its version history names TLS 1.2 support with version 4.0, so use a current version. | | Operating system | Exchange SE runs on Windows Server 2025, 2022 and 2019; Server Core is the recommended installation option (supportability matrix) | The POPcon requirements list the same three Windows Server versions, but do not mention Server Core. See “On the SE server or beside it” below. | | Upgrade path | In place from 2019 CU14 or CU15 only; “in-place upgrades from versions of Exchange Server earlier than Exchange Server 2019 are not supported” | From 2016 or 2013 the connector gets a new delivery target. | ### Why an SMTP-based connector does not depend on the Exchange version A POP3/IMAP connector such as POPcon is a Windows service that logs in to each provider mailbox, downloads the messages and hands them to Exchange the way any mail server would: over SMTP, to a receive connector. The knowledge base article Does POPcon work with Exchange 2010, 2007, 2003, 2000, 5.5, SBS editions? puts it in one sentence: “POPcon does not use Exchange-specific APIs — it communicates via SMTP, so version upgrades do not affect POPcon’s compatibility.” The POPcon system requirements list Exchange Server SE first among the compatible mail servers. On the connector side, the complete description of the Exchange server consists of three settings on the Exchange Server page : the server’s hostname or IP address, the SMTP port (25 by default), and Allow StartTLS . None of them names a version. On the Exchange side the counterpart is the receive connector that listens on port 25 with the Anonymous users permission group, plus the accepted domain for your mail domain; both are described for Exchange 2016, 2019 and SE on the same Microsoft pages, linked in the table above. Why Exchange has had no connector of its own since the Small Business Server editions is the subject of Does Exchange Server have a built-in POP3 connector? ### The upgrade paths, and what to do with the connector on each Microsoft’s page distinguishes three starting points. The connector work follows from whether the server stays the same. | Coming from | Microsoft’s path to SE | POP3/IMAP connector | | --- | --- | --- | | Exchange 2019 CU14 or CU15 | In-place upgrade directly to Exchange SE | Same server, same receive connector, same address in the connector. Nothing to reconfigure; run the three checks below. | | Exchange 2016 | No in-place upgrade. Legacy upgrade to Exchange 2019 CU14 or CU15 first, or a legacy upgrade directly to Exchange SE. Coexistence of 2016 with a 2019/SE organization is supported with Exchange 2016 CU23 on all 2016 servers ( system requirements ) | New server: set up its receive connector, then change the Exchange server address in the connector. Move the connector first if it runs on the old Exchange server. | | Exchange 2013 | “You must first perform a legacy upgrade to Exchange Server 2019 CU14 and fully remove Exchange Server 2013 from your organization. Only then can you proceed with an in-place upgrade” | The connector moves once, at the step to the 2019 server; the later in-place upgrade to SE leaves it alone. | ### After an in-place upgrade (2019 to SE): three checks - The Microsoft Exchange Transport service is started on the server. - The receive connector on port 25 still carries the Anonymous users permission group (EAC → Mail flow → Receive connectors → Default Frontend → Security). - Test Settings on POPcon’s Exchange Server page connects and gets an answer. If Exchange is not reachable while setup runs, the connector does not lose anything: according to the knowledge base article Will I lose emails if Exchange is down when POPcon tries to deliver? , POPcon keeps every message as a .msg file until Exchange has acknowledged it and retries on every retrieval cycle. If you stop the POPcon service for the duration of the upgrade instead, the mail simply waits in the provider mailboxes. ### After a legacy upgrade (new server): the order of work - Accepted domains. They are a global setting of the organization, so the new server already knows your mail domain. Confirm it under Mail flow → Accepted domains. - Receive connector on the new server. Receive connectors belong to the server they were created on. Enable Anonymous users on the new server’s Default Frontend connector as described in the configuration guide ; the steps and the reasoning are in How to download POP3 and IMAP mailboxes into Exchange 2016, 2019 and SE . POPcon always delivers without SMTP authentication. - Connector location. If POPcon runs on the old Exchange server, move it before that server is removed: install POPcon on the target machine, stop the service, copy popcon.config and all UIDS_*.dat files, start the service ( How can I transfer my POPcon configuration settings to a new server? ). The UIDS files are the record of what has already been downloaded. - Exchange server address. Enter the new server’s name or IP address in POPcon and use Test Settings . - Watch the first cycle. If Exchange answers with an error, the reply code tells you which of the steps above is missing: 550 5.7.1 Unable to relay points at the accepted domain or the receive connector permissions, and the other codes are in Exchange SMTP error codes explained . ### Outbound: MultiSendcon and the send connector MultiSendcon sits on the other side of Exchange: it is an SMTP relay that Exchange reaches through one send connector named “MultiSendcon” on port 2500, and it then picks the provider smart host by sender address. The product page lists Exchange Server SE as supported and notes that it “does not require Exchange agents or transport pipeline plugins”. After an in-place upgrade from 2019 the send connector is still the same object; check with Get-SendConnector that it is enabled and that its address space still carries the cost you set. With a new server, two properties of that send connector need a look. Its source servers — in Microsoft’s words “the Exchange servers where the Send connector is hosted” — must include the new server before the old one is removed. And its smart host address must be the IP address the MultiSendcon service listens on: the installation guide has you replace the default 127.0.0.1 with the address chosen on MultiSendcon’s Master relay tab, and 127.0.0.1 can only work while MultiSendcon runs on the same machine as the source server. If the connector has to be created again, the knowledge base has the command to create it manually . How Exchange chooses between send connectors is explained in Multiple smart hosts in Exchange 2016/2019 . ChangeSender , the Outlook add-in for choosing the sender address, lists Exchange 2000 through 2019 and Exchange Server SE on its product page. ### On the SE server or beside it Exchange SE is supported on Windows Server 2025, 2022 and 2019, and the POPcon requirements list all three, so the connector can run on the SE server itself. Two points speak for a separate machine when you are setting up a new server anyway. First, Microsoft marks Server Core as the recommended installation option for Exchange SE; the POPcon requirements name the Windows Server versions but say nothing about Server Core, so on a Core installation the member-server placement avoids the question. Second, a connector on its own machine keeps running through every Exchange cumulative update and holds the downloaded messages until Exchange is back. The trade-offs of the three placements are set out in Where to install a POP3/IMAP connector . If the move to SE is also the moment to reconsider the design as a whole — keep collecting from provider mailboxes, or point the MX record at the new server — the comparison is in POP3 retrieval or MX record to Exchange . ### Frequently asked questions ### Does Exchange Server SE have a built-in POP3 connector? No. Microsoft's POP3 and IMAP4 page for Exchange Server 2016, 2019 and Subscription Edition describes the two protocols as a way for clients to reach Exchange mailboxes; the services have to be started first. Neither that page nor Microsoft's lists of new and discontinued features in Exchange SE mention a component that fetches mail from external POP3 or IMAP mailboxes. For that you still run a separate connector service that submits the downloaded mail to Exchange over SMTP. ### Do I have to reconfigure my POP3 connector after the in-place upgrade from Exchange 2019 to SE? Nothing in POPcon's configuration refers to the Exchange version: it holds the Exchange server's address, the SMTP port (25 by default) and the StartTLS option. Microsoft describes Exchange SE RTM as code equivalent to Exchange Server 2019 CU15 apart from the licence agreement, the product name and the build number. After the upgrade, check that the Microsoft Exchange Transport service is running, that the receive connector on port 25 still has the Anonymous users permission group, and use Test Settings on POPcon's Exchange page. ### Can I upgrade from Exchange 2016 or 2013 directly to Exchange Server SE? Not in place. Microsoft states that in-place upgrades from versions earlier than Exchange Server 2019 are not supported. From Exchange 2016 you perform a legacy upgrade, that is a new server, either to Exchange 2019 CU14 or CU15 first or directly to Exchange SE. From Exchange 2013 you must first perform a legacy upgrade to Exchange 2019 CU14 and remove Exchange 2013 completely before the in-place upgrade to SE. In both cases the connector has to be pointed at the new server. ### Are Exchange Server 2016 and 2019 still supported? No. Microsoft's supportability matrix states that Exchange Server 2016 and Exchange Server 2019 reached end of support on October 14, 2025. Exchange Server Subscription Edition is listed on Microsoft's lifecycle page under the Modern Lifecycle Policy with a start date of July 1, 2025 and the status In Support. ### Do POPcon, MultiSendcon and ChangeSender work with Exchange Server SE? The POPcon system requirements list Exchange Server SE first among the compatible mail servers, and the MultiSendcon and ChangeSender product pages list Exchange Server SE as supported. POPcon and MultiSendcon exchange mail with Exchange over SMTP only: POPcon delivers to a receive connector, MultiSendcon receives from a send connector. Neither installs an agent into the Exchange transport pipeline. More in the Exchange mail flow guides , on the POPcon product page , the POPcon download page , the MultiSendcon download page or in the knowledge base . Auf Deutsch: Exchange Server SE (Subscription Edition) und POP3-/IMAP-Abholung: was sich ändert — und was nicht --- ## Exchange SMTP error codes explained: 421, 451, 452, 530, 550 Source: https://www.servolutions.com/guides/exchange-smtp-error-codes Language: en Exchange mail flow guides › Authentication and SMTP errors ### Exchange SMTP error codes explained: 421 4.4.1, 421 4.4.2, 451 4.7.0, 452 4.3.1, 530 5.7.1, 550 5.7.1 and more Exchange answers every SMTP submission with a three-digit reply code and an enhanced status code; 4.x.x means try again later and 5.x.x means the message was rejected, and the text after the code tells you which Exchange limit, permission or resource caused it. This page lists the replies a connector sees when it hands mail to an on-premises Exchange Server — a POP3/IMAP connector delivering into Exchange, or a relay taking Exchange’s outbound mail — with the usual cause, the fix, and the knowledge base article that has the commands and screenshots. Updated on 2026-09-26 ### How to read an Exchange SMTP reply A reply such as 550 5.7.1 Unable to relay has three parts. The reply code (550) is the classic SMTP status; the enhanced status code (5.7.1) is defined in RFC 3463 and, as Microsoft describes it for Exchange Server 2016, 2019 and Subscription Edition ( DSNs and NDRs in Exchange Server ), reads class.subject.detail : class 4 indicates a temporary delivery error and class 5 a permanent one; the subject groups the cause. The text after the code is what you search for — it names the limit or permission that fired. | Subject digit | Category (per RFC 3463, as listed by Microsoft) | Codes on this page | | --- | --- | --- | | x.3.x | Mail system (the destination mail system) | 452 4.3.1, 552 5.3.4 | | x.4.x | Network and routing | 421 4.4.1, 421 4.4.2 | | x.5.x | Mail delivery protocol | 503 5.5.2, 550 5.5.1, 554 5.5.2 | | x.7.x | Security or policy | 451 4.7.0, 454 5.7.3, 504 5.7.4, 530 5.7.0, 530 5.7.1, 550 5.7.1 | Two things follow from the class. A 4xx reply is not a rejection: the connector keeps the message and tries again on the next cycle, so a 4xx that repeats for hours is a configuration problem, not a transient one. A 5xx reply is final for that attempt; POPcon moves the message into its BADMAIL folder, and after the fix the message is retried from there (see the last question below). Where the code shows up is the connector’s log — for POPcon the file POPconSrv.log in the program directory. ### Temporary errors (4xx): Exchange wants you to try again | Reply | What it means | Typical cause when a connector submits mail | Fix | Article | | --- | --- | --- | --- | --- | | 421 4.4.1 Connection timed out | Exchange closed the SMTP connection before the submission finished | Very large messages or a slow network between the connector and Exchange | Raise the timeout on the receive connector: Set-ReceiveConnector -id "*default*" -ConnectionTimeout 01:00:00 , then restart the Microsoft Exchange Transport service | 421 4.4.1 Connection timed out | | 421 4.4.2 Message submission rate for this client has exceeded the configured limit | The receive connector’s MessageRateLimit — the maximum number of messages per minute from a single source — was reached; Microsoft’s default on the Default Frontend connector is unlimited ( Message rate limits and throttling ) | The limit was set too low for the volume the connector submits in one pass, for example after a best-practice tool changed it | List the connectors and their limits with Get-ReceiveConnector / ft name,messageratelimit , then raise the active one: Set-ReceiveConnector -identity Default* -MessageRateLimit 200 | 421 4.4.2 Message submission rate exceeded | | 451 4.7.0 Temporary server error. Please try again later. PRX | Exchange 2013 turns the session away for now; the article names two common causes | Two receive connectors in conflict, or TLS, DNS or network trouble on the Exchange server | Remove duplicate connectors and make sure the Default Frontend connector permits anonymous users; do not require TLS (the connector uses plain SMTP); disable unused network adapters, use IPv4 only, check DNS and the clock (NTP) | 451 4.7.0 Temporary server error PRX | | 452 4.3.1 Insufficient system resources | Exchange has paused mail acceptance because a monitored resource is short — Microsoft calls the mechanism back pressure ( Understanding back pressure ): under high pressure the transport service rejects all new incoming MAIL FROM commands | Free disk space on the Exchange server has run low; the knowledge base article names 4 GB as the point at which the older versions stop accepting mail | Free disk space (logs, temp files), or restart if memory was the resource; then move the .msg files from BADMAIL to PICKUP so the connector delivers them again | 452 4.3.1 Insufficient system resources | ### Permanent errors (5xx): Exchange rejected the message | Reply | What it means | Typical cause when a connector submits mail | Fix | Article | | --- | --- | --- | --- | --- | | 454 5.7.3 Client does not have permission to submit mail — or the connection is simply closed | Something between the connector and the Exchange transport refused the session | On Exchange 2007 the Windows SMTP service holding port 25, or the antispam agents; on Exchange 2003 sender, recipient or intelligent message filtering; anywhere, a firewall or antivirus product cutting the TCP connection | Stop and disable the Windows SMTP service; add the connector’s IP address to the antispam IP Allow List; switch off the Exchange 2003 filters; configure security products to drop mail silently instead of closing the connection | Connection unexpectedly closed / 454 5.7.3 | | 503 5.5.2 need Rcpt command | Exchange refused every recipient of the message, so the DATA command arrived without an accepted RCPT | Recipient filtering is on, the domain is not an accepted domain, or the address does not exist in Active Directory | Check Accepted Domains and the users’ addresses in Active Directory; on Exchange 2003 disable recipient filtering under Global Settings › Message Delivery | 550 5.5.1 user unknown / 503 5.5.2 need Rcpt | | 504 5.7.4 Unrecognized authentication type | Not from your Exchange: the Office 365 SMTP servers answer this when a relay talks to smtp.office365.com without the TLS mode they expect | MultiSendcon’s SMTP account for smtp.office365.com is set to plain SSL; Office 365 requires STARTTLS (explicit TLS on port 587), implicit SSL on 465 is not supported for outbound relay | Set the account’s SSL option to Explicit SSL/TLS (available since MultiSendcon 2.10) | 504 5.7.4 Unrecognized authentication type | | 530 5.7.0 Must issue a STARTTLS command first | The receive connector requires TLS before it accepts SMTP commands | TLS is enforced on the connector; the POP3/IMAP connector delivers over plain SMTP without STARTTLS | On the Default Frontend connector’s Security tab allow anonymous users and make sure TLS is offered, not required | 530 5.7.0 Must issue a STARTTLS command first | | 530 5.7.1 Client was not authenticated | The receive connector accepts only authenticated sessions | “Anonymous users” is not ticked in the connector’s permission groups — on Exchange 2007 and 2010 the receive connector accepts only authenticated sessions by default | Open the Default (or Default Frontend) receive connector, tick Anonymous users under Permission Groups; do not work around it with SMTP authentication | 530 5.7.1 Client was not authenticated | | 530 SMTP authentication is required | Not from Exchange at all: another mail server (typically hMailServer) is listening on port 25 of the address the connector delivers to | A second SMTP server on the same machine as the connector answers before Exchange does | Remove the other server, or move it to another port and set the connector’s Exchange delivery port to match (EXCHANGE tab in POPcon) | 530 SMTP authentication is required | | 550 5.5.1 user unknown | Exchange has no recipient with that address | The address is missing in Active Directory, the domain is not accepted, or a distribution group refuses external senders | Assign the address in Active Directory; for a group run Set-DistributionGroup GROUPNAME -RequireSenderAuthenticationEnabled $False ; on Exchange 2003 disable recipient filtering | 550 5.5.1 user unknown / 503 5.5.2 need Rcpt | | 550 5.7.1 Unable to relay | Exchange does not own the recipient domain and will not forward mail for it | Your internet domain is not in the list of accepted domains | Add the domain under Mail Flow › Accepted Domains as an Authoritative Domain ; on Exchange 2003 add it to the Default Policy under Recipient Policies | 550 5.7.1 Unable to relay ; guide: accepted domains and receive connector permissions | | 552 5.3.4 Header size exceeds fixed maximum size | The message header is larger than the receive connector allows | Mail from mailing lists, long forwarding chains or automated systems with very long headers | Set-ReceiveConnector -identity Default* -MaxHeaderSize 256kb , then move the affected messages from BADMAIL to PICKUP | 552 5.3.4 Header size exceeds fixed maximum size | | 554 5.5.2 No valid recipients | Exchange found no deliverable recipient for the message | Exchange 2000/2003: the internet domain is missing from the Default Policy, the connector’s machine has no relay rights on the virtual SMTP server, or the addresses are not assigned | Add the domain to the Default Policy under Recipients › Recipient Policies, grant relay rights, check the addresses in Active Directory | 554 5.5.2 No valid recipients | ### Three settings behind most of these replies Read across the two tables and the same three Exchange settings keep coming back. They are also the three steps of the setup guide How to download POP3 and IMAP mailboxes into Exchange 2016, 2019 and SE , which is why a fresh installation tends to produce these codes in this order. - Accepted domains. Exchange accepts SMTP mail only for domains it knows. A missing accepted domain produces 550 5.7.1 Unable to relay , and on the older versions 554 5.5.2 No valid recipients or 550 5.5.1 user unknown . The knowledge base explains why a connector needs the accepted domains . - Anonymous users on the receive connector. The connector delivers like any internet mail server would: plain SMTP, no login, no STARTTLS. If the receive connector requires authentication you get 530 5.7.1 Client was not authenticated ; if it requires TLS you get 530 5.7.0 Must issue a STARTTLS command first ; if two connectors compete on Exchange 2013 you get 451 4.7.0 PRX . The configuration guide for Exchange 2013 / 2016 shows the connector settings with screenshots. - Filtering and limits on the connector. Recipient and sender filtering (Exchange 2003) and the antispam agents (Exchange 2007) reject or drop sessions before the recipient is checked; the connector’s ConnectionTimeout, MessageRateLimit and MaxHeaderSize produce 421 4.4.1 , 421 4.4.2 and 552 5.3.4 . All three limits are changed with Set-ReceiveConnector in the Exchange Management Shell. Two replies in the tables do not come from your Exchange at all: 530 SMTP authentication is required is another SMTP server answering on port 25 of the connector’s machine, and 504 5.7.4 Unrecognized authentication type is the Office 365 side answering a relay such as MultiSendcon . In both cases changing Exchange changes nothing. ### Receive connector parameters that appear in the fixes | Parameter | Reply it produces when too low | Command from the knowledge base | Afterwards | | --- | --- | --- | --- | | ConnectionTimeout | 421 4.4.1 Connection timed out | Set-ReceiveConnector -id "*default*" -ConnectionTimeout 01:00:00 | Restart the Microsoft Exchange Transport service | | MessageRateLimit | 421 4.4.2 Message submission rate exceeded | Set-ReceiveConnector -identity Default* -MessageRateLimit 200 | Confirm with Get-ReceiveConnector / ft name,messageratelimit | | MaxHeaderSize | 552 5.3.4 Header size exceeds fixed maximum size | Set-ReceiveConnector -identity Default* -MaxHeaderSize 256kb | Move the rejected messages from BADMAIL to PICKUP | Default* matches the connector named Default ; if the connector that accepts the sessions is a different one — the Default Frontend connector on Exchange 2013 and later, or an SBS fax connector — apply the command to that connector, or to each connector listed by Get-ReceiveConnector . The header limit is not the limit on the size of the whole message: that one exists on the receive connector, for the organization and on the mailbox, and Messages over 10 MB are not arriving covers it. ### Frequently asked questions ### What is the difference between a 4xx and a 5xx reply from Exchange? The first digit of the reply and the first digit of the enhanced status code say the same thing: 4 is a temporary delivery error, 5 is a permanent one. Microsoft documents the classes for Exchange Server 2016, 2019 and Subscription Edition with reference to RFC 3463. A connector treats a 4xx reply as 'try again later' and keeps the message; a 5xx reply is a rejection, and the message is set aside for the administrator. ### Where do I see the error code Exchange returned? In the connector's log. POPcon writes every retrieval cycle, every message downloaded, the delivery status and any error to the text file POPconSrv.log in its program directory (C:\Program Files (x86)\POPcon); log size and rotation are set on the General tab of the configuration. The Exchange reply appears in the log line for the delivery attempt, usually one line below the recipient it was rejected for. ### Exchange closes the connection without any code. What then? An abrupt close is not an SMTP reply, so there is nothing to look up. The known causes are the Windows SMTP service competing with Exchange for port 25 on Exchange 2007, the Exchange antispam agents (add the connector's IP address to the IP Allow List), sender, recipient or intelligent message filtering on Exchange 2003, and firewalls or antivirus products that cut the TCP connection instead of silently dropping the mail. The article 'Exchange SMTP connection unexpectedly closed' walks through each. ### Should I enable SMTP authentication to get rid of 530 5.7.1 Client was not authenticated? No. The connector delivers over standard unauthenticated SMTP, and the fix is to allow anonymous users on the receive connector that accepts its connections. With authentication, Exchange shows every message delivered that way as sent by the account that logged in, which is not what you want for mail from external senders. ### What happens to a message Exchange rejected, and how do I retry it? POPcon moves a message Exchange has rejected into its BADMAIL folder inside the program directory. Once the cause is fixed, move the .msg files from BADMAIL into the PICKUP subfolder and the connector delivers them again. The articles for 452 4.3.1 and 552 5.3.4 describe this step. More in the Exchange mail flow guides , on the POPcon and MultiSendcon product pages, the POPcon download page or in the knowledge base . Auf Deutsch: Exchange-SMTP-Fehlercodes erklärt . --- ## 550 5.7.1 Unable to relay: the Exchange fix for a connector Source: https://www.servolutions.com/guides/exchange-unable-to-relay-receive-connector Language: en Exchange mail flow guides › Authentication and SMTP errors ### “550 5.7.1 Unable to relay” when a connector submits to Exchange: accepted domains and receive connector permissions Exchange answers 550 5.7.1 Unable to relay when an SMTP session without relay permission names a recipient whose domain is not an accepted domain of the Exchange organization. For a POP3/IMAP connector that delivers provider mail to your own mailboxes the fix is almost always the missing accepted domain, not a change to the connector software and not relay permission; relay permission on a receive connector is only needed for a host that must send through Exchange to recipients outside your domains. Updated on 2026-09-28 The Exchange behaviour on this page is taken from Microsoft Learn, where it is documented for Exchange Server 2016, 2019 and Subscription Edition; the connector side is taken from the POPcon knowledge base, whose article on this error covers Exchange 2003 to 2016. The reply is one row in our table of Exchange SMTP error codes ; this page is the long version of that row. ### What Exchange checks before it answers “Unable to relay” Every SMTP session arrives on a receive connector, and the receive connector gives the session a set of permissions. Microsoft’s description of the one that matters here ( Receive connectors in Exchange Server ): ms-Exch-SMTP-Accept-Any-Recipient “allows SMTP clients or servers to relay messages through the Receive connector. If this permission isn’t granted, only messages that are sent to recipients in accepted domains that are configured for the Exchange organization are accepted by the Receive connector.” So the reply depends on two things only: which permissions the session has, and whether the recipient’s domain is an accepted domain. | Session | Permissions the session receives (per Microsoft) | Recipient in an accepted domain | Recipient in any other domain | | --- | --- | --- | --- | | Anonymous — permission group Anonymous users | ms-Exch-Accept-Headers-Routing, ms-Exch-SMTP-Accept-Any-Sender, ms-Exch-SMTP-Accept-Authoritative-Domain-Sender, ms-Exch-SMTP-Submit — no relay permission | Accepted | 550 5.7.1 Unable to relay | | Anonymous, on a dedicated connector where the relay permission was added for NT AUTHORITY\ANONYMOUS LOGON | The four above plus ms-Exch-SMTP-Accept-Any-Recipient | Accepted | Accepted and relayed | | Externally secured — permission group Exchange servers with the authentication mechanism Externally secured | Includes ms-Exch-SMTP-Accept-Any-Recipient, and also ms-Exch-Bypass-Anti-Spam and ms-Exch-Bypass-Message-Size-Limit | Accepted | Accepted and relayed | The default connector for inbound mail, Default Frontend , listens on TCP port 25 for all IPv4 and IPv6 addresses and carries the permission group Anonymous users out of the box; Microsoft calls it “the common messaging entry point into your Exchange organization”. That is the first row of the table: mail for your accepted domains is taken, everything else is refused. It is the behaviour you want from a server that is reachable on port 25. ### Case 1: the connector delivers mail for your own mailboxes A POP3/IMAP connector such as POPcon downloads the messages from the provider mailboxes and hands them to Exchange over standard unauthenticated SMTP, the same way an internet mail server would. The recipients are your own users. If Exchange refuses them with 550 5.7.1 Unable to relay , Exchange does not regard their domain as its own. In the words of our knowledge base article “550 5.7.1 Unable to relay” error from Exchange : the internet domain has not been added to the list of accepted domains, and Exchange rejects delivery for any domain it does not own. This happens most often on a freshly installed server. When the first Exchange Mailbox server is installed, the fully qualified domain name of the Active Directory forest root domain is configured as the authoritative domain ( Accepted domains in Exchange Server ). If the forest is called company.local and the mailboxes at the provider are @company.com , the internet domain is simply not on the list yet. - Read the rejected recipient from the log. For POPcon the file is POPconSrv.log in the program directory. Note the domain part of the address Exchange refused. - Compare it with the accepted domains. In the Exchange admin center open Mail flow › Accepted domains , or run the command Microsoft gives for the check: Get-AcceptedDomain | Format-Table -Auto Name,DomainName,DomainType,Default,AddressBookEnabled . - Add the domain as an authoritative domain. Click Add , enter a descriptive name and the domain, and select Authoritative . In the Exchange Management Shell: New-AcceptedDomain -Name "Company internet domain" -DomainName company.com — the domain type defaults to Authoritative ( Procedures for accepted domains ). An accepted domain is either a single domain or a domain with subdomains ( *.company.com ); according to Microsoft the value cannot be changed from one form to the other afterwards. On Exchange 2003 the equivalent is the Default Policy under Recipients › Recipient Policies . - Check the connector’s own domain list. POPcon has a field Accepted Recipient Domains in its POP3/IMAP configuration. With a catch-all mailbox it uses this list to decide which recipients are local; the knowledge base explains why the connector needs the accepted domains . Enter the domain without the @ sign — company.com , not @company.com ( details ). - Deliver the rejected messages again. POPcon has moved them to its BADMAIL folder. Move the .msg files into the PICKUP subfolder and they are delivered in the next retrieval cycle ( how to resend them ). Nothing in these steps touches the permissions of the receive connector, and nothing needs to: the session is anonymous, the recipient is now in an accepted domain, and that combination is accepted. The complete setup, with the receive connector settings a connector does need (anonymous users, message size), is in How to download POP3 and IMAP mailboxes into Exchange and, with screenshots, in the Exchange 2013 / 2016 configuration guide . ### Which receive connector is answering? If the domain is on the list and the reply does not go away, make sure the session lands on the connector you think it does. Several receive connectors can listen on port 25 of the same server. Exchange picks the one whose remote IP address range is the most specific match for the connecting host; Microsoft’s example has one connector for 192.168.1.0-192.168.1.255 and one for 192.168.1.75 , and a connection from 192.168.1.75 is accepted by the second. A connector created years ago for a scanner or a fax service with a narrow range that happens to include the connector’s machine takes the sessions away from the Default Frontend connector — with whatever permission groups it was given. List what is there with the properties Microsoft uses for the same check: Get-ReceiveConnector | Format-List Name,Enabled,TransportRole,Bindings,RemoteIPRanges,PermissionGroups . In the Exchange admin center the ranges are on the Scoping tab of each connector under Mail flow › Receive connectors , the permission groups on the Security tab. ### Case 2: a host really has to relay to external recipients A different situation produces the same reply: a device or application on your network — Microsoft names web servers, database servers, monitoring applications and other network devices — submits mail to Exchange that is addressed to recipients on the internet. Here the accepted domains cannot help, because the recipient domains are not yours. The host needs the relay permission, and Microsoft’s procedure ( Allow anonymous relay on Exchange servers ) is strict about where it goes: - Create a dedicated receive connector . Microsoft: “Don’t attempt to add anonymous relay capability to the default Receive connectors that are created by Exchange.” - Create it in the Front End Transport service (role Frontend Transport , type Custom ), bound to port 25. - Under Remote network settings remove the entry 0.0.0.0-255.255.255.255 and enter only the IP addresses of the hosts that may relay. Microsoft’s advice is to err on the side of being too specific. In the shell the same connector is created with New-ReceiveConnector -Name "Anonymous Relay" -TransportRole FrontendTransport -Custom -Bindings 0.0.0.0:25 -RemoteIpRanges 192.168.5.10,192.168.5.11 . Then the permission is granted in one of two ways — one or the other, not both: | Method | How it is configured | What Exchange treats the host as | Consequences named by Microsoft | | --- | --- | --- | --- | | Anonymous with relay permission | Exchange Management Shell only: Set-ReceiveConnector "Anonymous Relay" -PermissionGroups AnonymousUsers , then Get-ReceiveConnector "Anonymous Relay" / Add-ADPermission -User "NT AUTHORITY\ANONYMOUS LOGON" -ExtendedRights "Ms-Exch-SMTP-Accept-Any-Recipient" | An anonymous sender | Grants the minimum required permissions; messages do not bypass antispam or message size limit checks; the sender address is not resolved to a display name in the global address list | | Externally secured | Exchange admin center, Security tab: authentication Externally secured , permission group Exchange servers ; or Set-ReceiveConnector "Anonymous Relay" -AuthMechanism ExternalAuthoritative -PermissionGroups ExchangeServers | An authenticated, completely trusted sender | Easier to configure; messages bypass antispam and message size limit checks; the host can submit messages as if they originated from internal senders | A POP3/IMAP connector that only delivers inbound mail belongs to case 1 and does not need such a connector. The knowledge base shows how to have individual addresses forwarded to a mailbox on the internet with a mail contact in Exchange, which leaves the forwarding to Exchange itself. ### Testing the receive connector by hand Microsoft’s test for the relay connector works for case 1 as well, and it shows the reply at the exact command that triggers it. From the machine the connector runs on, open a command prompt with the Telnet client installed: - telnet , then OPEN 25 - EHLO - MAIL FROM:sender@example.org - RCPT TO:user@company.com The answer to RCPT TO is the result: 250 2.1.5 Recipient OK means Exchange accepts that recipient from this host, 550 5.7.1 Unable to relay means it does not. Repeat the command with a recipient in each of your domains; a domain that is refused is a domain missing from the accepted domains. QUIT ends the session without sending anything. ### Replies that look similar and are not | Reply | What is different | Where the fix is | | --- | --- | --- | | 550 5.7.1 Unable to relay | The recipient’s domain is not an accepted domain and the session has no relay permission | Accepted domains (case 1) or a dedicated relay connector (case 2) | | 530 5.7.1 Client was not authenticated | The receive connector accepts only authenticated sessions; the recipient has not been looked at yet | Tick Anonymous users on the receive connector ( article ) | | 550 5.5.1 user unknown | The domain is accepted, but no recipient has that address | Assign the address in Active Directory ( article ) | | 503 5.5.2 need Rcpt command | Every recipient of the message was refused before, so no recipient was left when the message body was announced | Look at the reply to the recipient one line earlier in the log ( article ) | ### Frequently asked questions ### Does a POP3 connector need relay permission on the receive connector? Not for mail addressed to your own mailboxes. Microsoft describes the relay permission (ms-Exch-SMTP-Accept-Any-Recipient) as the one that lets a host relay through the receive connector; without it, Exchange still accepts messages for recipients in the accepted domains of the organization. A connector that delivers provider mail to local mailboxes therefore needs the domain in the accepted domains list and anonymous users allowed on the receive connector, nothing more. ### Should I switch the connector to SMTP authentication so that Exchange lets it relay? No. POPcon delivers over standard unauthenticated SMTP. With authentication, Exchange shows every message delivered that way as sent by the account that logged in, which is wrong for mail from external senders. Add the missing accepted domain instead. ### Can I add the relay permission to the Default Frontend receive connector? Microsoft advises against it: do not add anonymous relay capability to the default receive connectors that Exchange creates. The Default Frontend connector listens for connections from any source on port 25, so relay permission there would turn the server into an open relay. Create a dedicated receive connector that lists only the IP addresses allowed to relay. ### Which receive connector answers my connector's connection? The one whose remote IP address range is the most specific match for the connecting host. Microsoft's example: with one connector for 192.168.1.0-192.168.1.255 and another for 192.168.1.75, a connection from 192.168.1.75 is accepted by the second. A forgotten connector with a narrow range can therefore take the sessions away from the Default Frontend connector. ### What happens to the messages Exchange rejected with 550 5.7.1? POPcon moves a message whose delivery failed into its BADMAIL folder inside the program directory. After you have added the accepted domain, move the .msg files from BADMAIL into the PICKUP subfolder; POPcon picks them up in the next retrieval cycle and delivers them again. More in the Exchange mail flow guides , on the POPcon product page, the POPcon download page or in the knowledge base . Auf Deutsch: 550 5.7.1 Unable to relay bei der Übergabe an Exchange . --- ## Gmail into Exchange over IMAP with OAuth2 Source: https://www.servolutions.com/guides/gmail-oauth2-imap-into-exchange Language: en Exchange mail flow guides › Authentication and SMTP errors ### Fetching Gmail and Google Workspace mail into Exchange over IMAP with OAuth2 Google requires OAuth 2.0 for third-party access to Gmail and Google Workspace mailboxes; a connector signs in once through a Google consent page and then downloads from imap.gmail.com on port 993 with a token that it refreshes itself, instead of a stored password. This guide explains what Google switched off and when, what that means for a POP3/IMAP connector that feeds an on-premises Exchange Server, and the eight steps that connect a Gmail or Google Workspace mailbox with OAuth2. Updated on 2026-09-24 ### What Google switched off Google calls an application that signs in to a Google account with only a username and password a “less secure app”. For Google Workspace accounts the administrator help page Control access to less secure apps states it in one sentence: starting 1 May 2025, Workspace accounts no longer support less secure apps, third-party apps or devices that sign in with a username and password, and OAuth must be used instead. The companion page Transition from less secure apps to OAuth gives the first cut-off — since 14 March 2025 users must use OAuth with third-party apps to access Gmail — and names the one exception: app passwords. Google’s advice there for anything else is short: ask the app developer to update the app to OAuth 2.0. For a personal Google account the rules are softer but point the same way. Google’s page Less secure apps & your Google Account tells users to switch to a type of access that does not share password data, and says Google might block anyone trying to sign in from an app that does not meet its security standards. Its page on app passwords describes them as 16-digit codes available only with 2-Step Verification turned on, and adds that they are not recommended and unnecessary in most cases. Since January 2025 IMAP is always on for personal Gmail accounts; the old “Enable IMAP” switch is gone ( Gmail IMAP help ). | Sign-in method | Google Workspace account | Personal @gmail.com account | Where Google documents it | | --- | --- | --- | --- | | Username and password in the app (“less secure app”) | Not supported since 1 May 2025 (first-time connections refused since March 2025) | Discouraged; Google may block the sign-in | Control access to less secure apps; Less secure apps & your Google Account | | App password (16 digits, needs 2-Step Verification) | Still possible for devices that only speak SMTP/IMAP/POP3, by the administrator’s choice | Possible, “not recommended and unnecessary in most cases” | Transition page; Sign in with app passwords | | OAuth 2.0 (“Sign in with Google”) | Required | Recommended | Transition page; Gmail IMAP help | | IMAP access itself | Available | Always on since January 2025 | Gmail IMAP help | ### What this means for a connector A POP3/IMAP connector is exactly the kind of “third-party app” Google means: a Windows service that logs in to the mailbox on a schedule, downloads what is new and hands it to Exchange over SMTP. If it does that with a stored password, a Workspace mailbox has refused it since May 2025 and a personal mailbox may refuse it at any time. With OAuth 2.0 the sequence is different, and the difference is what makes the setup a one-time event rather than a recurring support ticket: - The sign-in happens once, in a browser on the connector’s machine. Google shows its consent page, names the application, lists what it may do with the mailbox — read, compose and delete email — and asks the account owner to agree. - The connector keeps a token, not a password. After the consent the connector stores an OAuth token and refreshes it automatically. Changing the Google password does not touch it, and nothing password-shaped is written into the connector’s configuration. - The token is presented instead of a password when the connector logs in to imap.gmail.com. Everything else about IMAP is unchanged: folders, downloading, the delete-after-download or leave-on-server behaviour set for the account, and the schedule. - The Exchange side does not change at all. Delivery into Exchange runs over SMTP through the receive connector, as for every other account; see How to download POP3 and IMAP mailboxes into Exchange Server 2016, 2019 and SE . The same pattern applies to Microsoft 365 with a Microsoft sign-in; the mechanics of tokens and consent are described in Basic authentication is gone: fetching a Microsoft 365 mailbox by IMAP or POP3 with OAuth2 into Exchange . ### Step by step: a Gmail or Google Workspace mailbox in POPcon The steps below are the ones from the knowledge-base article How to connect to Gmail with modern authentication / OAuth2 , which carries a screenshot of each screen. POPcon has supported OAuth 2.0 for Google and Microsoft accounts since version 4.8.1 (September 2024). - Add the mailbox as IMAP on imap.gmail.com, port 993. In the connector, add a new mailbox account, set the server type to IMAP, the server address to imap.gmail.com and the port to 993. The port for Gmail IMAP with OAuth2 is 993, not the plain-IMAP default 143. - Click “Connect OAuth2” next to the authentication field. Leave the password field empty. The connector opens a browser window on that machine. - Sign in to the Google account. Use the Google account that owns the mailbox to be fetched: a personal @gmail.com address or a Google Workspace user. - Grant the connector permission to access the mailbox. Google lists what the application will be able to do with the mailbox: read, compose and delete email. The application is named “POPcon email forwarding”. Tick the permission and click Continue. - If Google shows an “unverified app” warning, click Advanced and proceed. The knowledge-base walkthrough notes that Google may show this warning while its verification of the application is pending. Click Advanced, then “Go to POPcon email forwarding (unsafe)” to continue. - Complete the authentication flow. Google shows the requested permissions once more; confirm. A confirmation page appears and the browser window can be closed. - Check that the status reads “Authenticated”. Back in the connector the account status changes to Authenticated. The OAuth token is stored and refreshed automatically from now on. - Run “Test access”. The test logs in to Gmail with the token. If it passes, the account is ready and the schedule takes over. No password is entered at any point; the OAuth token is stored securely and refreshed automatically. The walkthrough contains no step in which you register anything in your Google account or in the Google Workspace admin console: the sign-in consents to the connector’s own registered application, which is why Google’s consent page says “POPcon email forwarding” rather than the name of your organisation. ### IMAP or POP3 at Google? Google offers both. The POPcon walkthrough with OAuth2 uses IMAP; the older knowledge-base article Can POPcon download email from Gmail accounts? describes the legacy POP3-SSL setup with a password or app password and points to the OAuth2 walkthrough as the recommended path. | | IMAP with OAuth2 (recommended) | POP3 with a password or app password (legacy) | | --- | --- | --- | | Server and port | imap.gmail.com, 993, IMAP-SSL | pop.gmail.com, 995, POP3-SSL ( Google’s POP settings ) | | Authentication | OAuth2 Google — one sign-in, token refreshed by the connector | Gmail password or a 16-digit app password (2-Step Verification required) | | Google Workspace | Works | Password refused since 1 May 2025; app password only where the administrator allows it | | What happens to the copy at Google | Set per account in the connector: delete after download or leave on the server | Google’s POP settings decide: keep the copy in the inbox, mark it as read, archive it or delete it; “recent mode” ( recent: before the user name) shows the last 30 days | | Availability of the protocol | Always on for personal accounts since January 2025 | Enabled in Gmail’s Forwarding and POP/IMAP settings | ### Symptoms, and what each one really means | What you see | Cause | What to do | | --- | --- | --- | | Login to a Google Workspace mailbox fails although the password is correct | Google no longer accepts a username and password from a third-party app (since 1 May 2025) | Set the account to IMAP, imap.gmail.com, 993, click Connect OAuth2 and sign in once. | | Google shows “This app isn’t verified” during the sign-in | Google’s verification of the application is pending, as the walkthrough notes | Click Advanced , then Go to POPcon email forwarding (unsafe) , and finish the consent. | | An app password cannot be created in the Google account | App passwords exist only for accounts with 2-Step Verification turned on | Do not go that way: use Connect OAuth2 ; no app password is needed. | | The sign-in succeeded, but the status does not read Authenticated | The browser flow was not completed, or the wrong Google account was chosen | Click Connect OAuth2 again, pick the account that owns the mailbox, complete every consent page, then run Test access . | | Mail arrives in Exchange but stays in the Gmail inbox as well | The account is set to leave messages on the server | Intended during a migration; otherwise change the account’s delete / leave-on-server setting in the connector. | ### Frequently asked questions ### Do I need a Google app password for the connector? No. With OAuth2 the connector never sends a password to Google; it signs in once through Google’s consent page and works with a token afterwards. Google itself says app passwords are not recommended and unnecessary in most cases; they are 16-digit codes that exist only for accounts with 2-Step Verification turned on, and Google’s own instruction to app developers is to update the app to OAuth 2.0. The older POPcon article for Gmail with a password or app password over POP3 still exists, but the OAuth2 walkthrough is the recommended path. ### Which server and port does the connector use for Gmail? IMAP on imap.gmail.com, port 993 (IMAP over SSL/TLS), with the authentication set to OAuth2 Google. Google’s POP3 endpoint is pop.gmail.com on port 995 with SSL; the POPcon walkthrough with OAuth2 uses IMAP. ### Does this work for Google Workspace as well as a personal Gmail account? Yes, the sign-in is the same. For Google Workspace it is the only path: Google’s administrator help states that since 1 May 2025 Workspace accounts no longer support apps that sign in with only a username and password, and that OAuth must be used. For a personal Google account Google steers to “Sign in with Google” in the same way and may block sign-ins from an app that does not meet its security standards. ### Will the connector ask me to sign in again later? Not as part of normal operation. The knowledge-base walkthrough states that the OAuth token is stored securely and refreshed automatically, and no password is entered at any point. A new sign-in is needed only when the consent no longer exists, for example after the account owner has removed the application’s access in the Google account settings, or when the mailbox is moved to a different Google account. ### Can I keep using POP3 with Gmail instead of IMAP? Google still documents POP on pop.gmail.com, port 995 with SSL, including its “recent mode” (the user name prefixed with recent:) that shows the last 30 days of mail. The POPcon walkthrough with OAuth2, however, is written for IMAP on imap.gmail.com, port 993; the older POP3-SSL article for Gmail relies on a password or app password. For a new setup, take IMAP with OAuth2. More in the Exchange mail flow guides , on the POPcon product page , the download page or in the knowledge base . Auf Deutsch: Gmail und Google Workspace per IMAP mit OAuth2 nach Exchange abholen . --- ## IONOS, Strato or GMX as Exchange smart host: sender rules Source: https://www.servolutions.com/guides/ionos-strato-gmx-smart-host-exchange Language: en Exchange mail flow guides › Outbound: send connectors and smart hosts ### Using IONOS, Strato or GMX as the smart host for Exchange: why the sender must match the login, and how to send several domains anyway A provider mailbox used as the smart host for Exchange is an authenticated SMTP account, and IONOS documents that since January 2024 its outgoing mail servers accept a message only when the sender address is in the same domain as the mailbox used for the login; a message with another sender, or with no sender at all, is refused with Sender address is not allowed . An Exchange Server that sends several domains through one provider login therefore gets every other domain rejected, and its non-delivery reports and out-of-office replies with it. The fix is one authenticated relay session per sender domain, which Exchange cannot do on its own: it authenticates a send connector with one login for everyone. Updated on 2026-09-18 ### The setup that breaks Many small Exchange installations do not deliver outbound mail themselves. The send connector points at the provider’s outgoing mail server as a smart host, authenticates with the credentials of one mailbox there, and the provider takes care of DNS, reputation and TLS towards the world. That works as long as every sender in Exchange writes from the domain of that one mailbox. It stops working the moment a second domain is added to Exchange, a user replies from an alias in another domain, or Exchange itself sends a message with an empty sender. The provider sees a sender it does not own behind the login it authenticated, and rejects the message at the MAIL FROM step of the SMTP session. Exchange keeps the message in its queue with the provider’s error text, and the sender learns about it from a delayed-delivery notification, if at all. ### What IONOS enforces, in its own words IONOS describes the change on its help page Wichtige Änderung für das Versenden von E-Mails mit abweichender Absenderadresse (German), and our knowledge base records the effect on Exchange in IONOS blocks non-delivery reports and out-of-office messages : | Rule | What it means for Exchange | Source | | --- | --- | --- | | Sender domain must equal the login mailbox domain | Since 29 January 2024 the outgoing servers for Mail Basic and Mail Business refuse alternative sender addresses. The local part before the @ may differ; the domain after it may not. Each Exchange domain needs a login in that domain. | IONOS help page | | Empty sender addresses are refused | Non-delivery reports and out-of-office replies leave Exchange with an empty envelope sender and are rejected with Sender address is not allowed . Not configurable in Exchange. | IONOS help page, knowledge base | | Applies to mail servers and relays, not only to mail clients | IONOS names Outlook, mobile apps and server applications such as Microsoft 365/Exchange and Open-Xchange alike, and states that alternative sender addresses are not possible on IONOS Microsoft Exchange either. | IONOS help page | | A relay needs a mailbox plus an SPF record in the same domain | The section for SMTP relay servers and smart hosts asks for a relay mailbox address and an IONOS SPF entry for that domain. | IONOS help page | ### What about Strato, GMX and the others? We document what we can verify. For Strato the knowledge base holds one fact: the Strato outgoing servers have required SMTP authentication since September 2008 ( knowledge base, German ), so an unauthenticated send connector fails there with 530 SMTP authentication is required . Which sender addresses Strato, GMX or web.de accept behind a login is published on their own help pages and is not reproduced here; check the page for your product before you rely on it. The symptom class is the same whatever the wording: a permanent error at MAIL FROM that names the sender address, for exactly the messages whose sender is not the login. The relay setup below fixes that class, because it makes every session use the login that owns the sender. ### Symptom, cause, fix | What you see | Cause | Fix | | --- | --- | --- | | Sender address is not allowed in the Exchange queue, only for the second domain | The send connector authenticates with the first domain’s mailbox for every sender | One relay account per sender domain, each with that domain’s login | | External senders never receive your non-delivery reports or out-of-office replies | Empty envelope sender, rejected by the provider | A relay that replaces the empty sender; the LITE edition is enough | | Sending works from Outlook with the provider account, but not from Exchange | Outlook logs in as the mailbox that owns the address; Exchange uses one connector login for all | Same as the first row: the login must follow the sender | | 530 SMTP authentication is required | The connector sends without credentials to a server that demands them | Add the login to the connector or to the relay account ( knowledge base ) | ### Fix A: stay with one domain If Exchange really sends only one domain, keep the send connector as it is, authenticate it with a mailbox in that domain and make sure no user has a reply address elsewhere. What remains is the empty-sender case: Exchange offers no setting that puts an address into the envelope of a non-delivery report or an out-of-office reply, so external senders will not get them through IONOS unless something between Exchange and the provider fills the sender in. That is the single-account job the lower-priced MultiSendcon LITE edition does. When Exchange behind a POP3 connector generates such a report in the first place is covered in NDRs for external senders behind a POP3 connector . ### Fix B: one relay session per sender domain Exchange chooses a send connector by recipient domain and cost, never by sender (see why send connectors cannot route by sender ), so the per-sender decision has to happen in front of the provider. MultiSendcon runs as a Windows service on the Exchange server, receives everything through one send connector and matches the sender address against its relay accounts: - Install. Download MultiSendcon and run the installer on the Exchange server. It creates the send connector that hands outbound mail to the service; if PowerShell remoting is disabled, one command creates it manually ( knowledge base ). - One SMTP account per domain. Under Relay servers add an SMTP account for each provider login: server, port (25, 587 or 465; SSL is switched on automatically with 465), user name and password, and the sender filter *@company-a.com . Repeat for *@company-b.com with the login that owns that domain, even when both live at the same provider. - Fill the empty sender. In each account, set the fixed sender address replacement so that messages without a sender leave with an address the provider accepts; where the message header names a sender, that address is used instead of the fixed one. - Test. Run the account test with a From address that matches each sender filter and read the reply in the Administrator log. - Switch Exchange over. Lower the cost of the MultiSendcon send connector from 100 to 1 so it wins over the old provider connector, then disable the old one. From now on each domain reaches the provider through its own login, and senders that match no account fall through to the Master Relay. Accounts are matched top to bottom, so a single address can sit above its domain rule, and two accounts with the same filter act as primary and fallback. The step-by-step guide for multiple smart hosts shows the same setup next to the native per-recipient-domain configuration. ### Next steps - Two domains at IONOS: create the second mailbox, then install the trial and add two accounts with the two logins and sender filters. - One domain, but missing non-delivery reports: the lower-priced LITE edition is enough; set one account with the fixed sender. - Not sure what the provider rejects: run the account test and read the exact server reply in the log before changing Exchange. - Two companies at two different providers on one server: Hosting several companies or domains on one Exchange Server covers the accepted domains, the address policies and the relay account per company. ### Frequently asked questions ### Can I keep sending from an address in another domain through my IONOS login? Not through IONOS Mail Basic or Mail Business: since January 2024 the part of the sender address after the @ must be the same domain as the mailbox used for the SMTP login, and IONOS also states that alternative sender addresses are not possible on its hosted Microsoft Exchange. The part before the @ stays free. For every additional domain you need a login that belongs to that domain, and something in front of the provider that picks the right login per sender. ### Why do my non-delivery reports and out-of-office replies never reach external senders? Exchange sends both with an empty envelope sender (an empty MAIL FROM), exactly as the SMTP standard requires, and IONOS rejects messages with an empty sender since January 2024. Nothing in Exchange changes this behaviour. A relay between Exchange and the provider can fill the empty sender with the address from the message header, or with a fixed address configured for the account, and the message is then accepted. ### Is the lower-priced MultiSendcon LITE edition enough? For one provider login it is: LITE handles a single relay account and replaces the empty sender, which is the whole fix for the non-delivery-report and out-of-office case. It has no per-sender routing, so as soon as two domains must leave through two different logins you need the full edition with one SMTP account per sender domain. ### Which port and encryption should the relay account use? The account settings accept port 25, 587 or 465; with port 465 the encrypted connection is switched on automatically. Use the port and the login your provider publishes for its outgoing mail server, then run the built-in account test with a sender address that matches the account's sender filter before you switch the Exchange send connector over. More on outbound mail flow in the Exchange mail flow guides , or in the knowledge base . Auf Deutsch: IONOS, Strato oder GMX als Smarthost für Exchange . --- ## Several domains on one Exchange Server: inbound and outbound Source: https://www.servolutions.com/guides/multiple-domains-one-exchange-server Language: en Exchange mail flow guides › Outbound: send connectors and smart hosts ### Hosting several companies or domains on one Exchange Server: separate inbound mailboxes and outbound relays One Exchange Server can serve several domains. Inbound, each domain is an accepted domain with its own provider mailboxes or its own MX record; outbound, each domain must leave through the relay that is allowed to send for it — and that is where Exchange falls short, because it selects a send connector by the recipient’s domain and never by the sender. The inbound side is configuration that Exchange has built in; the outbound side needs a relay that routes by sender, such as MultiSendcon. Updated on 2026-10-05 The Exchange behaviour on this page is taken from Microsoft Learn, where it is documented for Exchange Server 2016, 2019 and Subscription Edition; the connector and relay side is taken from the POPcon and MultiSendcon pages, help and knowledge base. ### What “several domains” means to Exchange Exchange does not know companies. It knows one organization, a list of accepted domains, and recipients with email addresses. Microsoft’s Accepted domains in Exchange Server puts it in one sentence: “Accepted domains are a global setting for the Exchange organization, and you can have multiple accepted domains of the same or different types.” And for the usual case: “An organization can be configured with multiple authoritative domains.” So two companies on one server are, technically, two accepted domains and two groups of mailboxes whose addresses end differently. Which type each domain gets depends on where its recipients are: | Accepted domain type | When Microsoft says to use it | Non-delivery reports for unknown recipients | Usable in email address policies | | --- | --- | --- | --- | | Authoritative | “when all recipients in that domain exist in your Exchange organization” | Exchange is responsible for generating them | Yes | | Internal relay | Some of the recipients do not exist in the organization, for example “you share the domain between the Exchange organization and a third-party messaging system” | Exchange is not responsible; a send connector with the domain’s address space relays the rest | Yes | | External relay | “None of the recipients in the external relay domain exist in the Exchange organization” | Exchange is not responsible | No | A company whose mailboxes all live on your server gets an authoritative domain. Microsoft’s procedures page gives the two ways to add one: in the Exchange admin center under Mail flow › Accepted domains , or in the Exchange Management Shell: - New-AcceptedDomain -Name "Company B" -DomainName company-b.com — the type defaults to Authoritative. - Get-AcceptedDomain | Format-Table -Auto Name,DomainName,DomainType,Default,AddressBookEnabled — Microsoft’s own check of what is configured. A domain that is missing from this list is the classic cause of 550 5.7.1 Unable to relay when a connector submits mail for it; that case is described in 550 5.7.1 Unable to relay when a connector submits to Exchange . ### One address per user in the right domain: email address policies Accepting a domain does not yet give anybody an address in it. That is the work of email address policies, which Microsoft describes as “the rules that create email addresses for recipients in your Exchange organization” ( Email address policies in Exchange Server ). Three of their properties matter with several companies: - The recipient filter “specifies the recipients whose email addresses are configured by the policy”. The precanned filters can select by recipient type, Company, Department, State or Province and the custom attributes 1 to 15. “Property values require an exact match”: a Company value of Company B does not match Company B Ltd . - The primary address. One template in a policy defines the primary SMTP address, and Microsoft calls it “the Reply-To: email address for recipients”. This is the address the user sends from, and therefore the address the outbound relay will see. - The priority. “If a recipient is identified by multiple email address policies, the recipient’s email addresses are only configured by the first email address policy that’s evaluated”, a lower number is evaluated first, and “the default email address policy is always evaluated last”. The policy for the second company therefore needs a higher priority than the default policy, or its users keep the first company’s address. A practical arrangement is one policy per company, filtered by the Company attribute of the user accounts, each with its own domain in the primary address template. ### Inbound: getting each domain’s mail to the server There are two ways for a domain’s mail to reach Exchange, and they can be mixed per domain. Either the domain’s MX record points at your server and mail arrives by SMTP, or the mail stays in mailboxes at the provider and a connector collects it. The choice between the two is the subject of POP3 retrieval or MX record to Exchange ; nothing about it changes with a second domain, except that it is made once per domain. For the collected domains, POPcon is a Windows service that downloads mail from POP3 and IMAP mailboxes and submits it to Exchange over SMTP. Its account settings define the type per account: - Single User: “All emails from this account are delivered to a single Exchange mailbox.” One provider mailbox per person, in whichever domain it belongs to. Nothing needs to be told apart: the account says where the mail goes. - Catch-All: “Emails are distributed to multiple Exchange mailboxes based on recipient address analysis.” One provider mailbox per domain collects everything for that domain. With two companies this means two catch-all accounts, one at each provider. Catch-all accounts need one more setting. A single download can contain mail for many recipients, and POPcon “must decide which recipients are local (to be delivered to Exchange) and which are not”. The field Accepted Recipient Domains on the POP3/IMAP configuration tab lists the domains POPcon should handle; the knowledge base article Why does POPcon need to know the accepted domains? describes what happens without it: delivery attempts to unknown addresses, Exchange errors, or everything re-routed to the postmaster. When a second company is added, its domain goes into this field as well as into Exchange. What catch-all mailboxes can and cannot do in general is covered in Catch-all mailbox or one POP3 mailbox per user . ### When the server holds only part of a domain A branch office, or a company that keeps some mailboxes at the provider, has only part of a domain on the Exchange server. An authoritative domain is then the wrong type by Microsoft’s definition, because not all recipients exist in the organization: Exchange would answer mail to the colleagues at the provider with a non-delivery report instead of sending it out. Microsoft’s answer is the internal relay domain together with a send connector for that domain’s address space. The POPcon knowledge base describes a second arrangement for the collecting side in Configuring POPcon for a branch office that handles only part of a domain : Exchange accepts an internal domain such as branchoffice.local ; the branch users get two SMTP addresses, the company address as the default reply address and one in the internal domain; and in POPcon’s catch-all settings “Auto replacement of recipient domains” rewrites the incoming company domain to the internal one. Users keep sending from the company address, and Exchange no longer considers the company domain its own. ### Outbound: why one smart host is not enough Inbound, the domains never get in each other’s way. Outbound they do, because all mail of the server leaves by the same rules. Exchange chooses a send connector by the recipient’s domain, the connector’s address space, and by cost and scope; Microsoft’s connector selection rules contain no criterion for the sender. A second send connector with the second company’s smart host therefore does not send the second company’s mail; the details and the attempts that fail are in Exchange send connectors route by recipient domain, not sender . This matters as soon as the provider checks who is sending. A provider relay is an authenticated account, and providers tie the permitted sender addresses to that account. IONOS documents the rule: since January 2024 its outgoing servers accept a message only when the sender address is in the domain of the mailbox used for the login. Company B’s mail sent through company A’s login is refused with Sender address is not allowed ( Using IONOS, Strato or GMX as the smart host for Exchange ). MultiSendcon is a Windows service that receives all outbound mail from Exchange through one send connector and forwards each message through the SMTP relay account that matches its sender. What can be set per account is listed on its help page for SMTP account settings : | Per relay account | What it is for with several companies | | --- | --- | | SMTP server, port, user name and password | Each company’s own provider relay and login; ports are “typically 25, 587, or 465” | | Sender Address Filter | *@company-a.com for all senders of a domain, or user@company-a.com for one address; left blank, the account matches all senders | | Recipient Address Filter | Restricts an account to certain recipients, in the same format | | Local IP Address | On a system with several network cards, which card handles this account — a separate outgoing address per company where that is required | | HELO/EHLO Domain | The name the relay session announces itself with, per account | | Fixed Sender Address Replacement | Replaces the sender with a fixed address where a provider requires the address of the authenticated account | The order of the accounts decides when more than one matches: “the topmost entry in the list takes priority” ( Relay Servers configuration ). An account with an empty sender filter at the bottom of the list therefore catches every sender that no company account claimed. On the Exchange side nothing is company-specific: one send connector for all domains points at the address and port MultiSendcon listens on, by default port 2500, and the installer can create it. The step-by-step setup is in Multiple smart hosts in Exchange 2016/2019 . Non-delivery reports and automatic replies are a special case, because Exchange sends them with an empty sender that belongs to no company. What a provider does with them, and how the relay fills in a sender, is described in NDRs for external senders behind a POP3 connector . ### A worked example: two companies, two providers Company A has its domain and mailboxes at IONOS, company B at a second provider. Both work on the same Exchange Server. | Setting | Company A | Company B | | --- | --- | --- | | Accepted domain in Exchange | company-a.com , authoritative | company-b.com , authoritative | | Email address policy | Recipient filter Company = Company A, primary address in company-a.com | Recipient filter Company = Company B, primary address in company-b.com | | Inbound collection (POPcon) | Accounts at provider A, Single User or Catch-All | Accounts at provider B, Single User or Catch-All | | Accepted Recipient Domains (POPcon, for Catch-All) | Both domains listed | | Send connector in Exchange | One connector for all domains, pointing at MultiSendcon | | Relay account (MultiSendcon) | Provider A’s SMTP server, login of a mailbox in company-a.com , sender filter *@company-a.com | Provider B’s SMTP server, login of a mailbox in company-b.com , sender filter *@company-b.com | A workable order: add the second accepted domain and the address policy first and check that the users of company B show the right primary address; then add the collecting accounts and the domain in POPcon and send a test message to each domain from outside; then install MultiSendcon, add one relay account per company, use the built-in account test , and send one message from a user of each company to an external address. The headers of the two received messages show which provider relayed each of them. ### What stays shared Two companies on one Exchange organization are not two tenants. Three things remain common, and it is better to know them before promising separation to either company: - The accepted domains and the default domain. Accepted domains are organization-wide, and “one accepted domain is always configured as the default domain”. Microsoft lists what it is used for, among other things “the external postmaster address: postmaster@ ”. There is only one. - The address book. Without further configuration every user sees every other user in the global address list. Microsoft’s address book policies let administrators “segment users into specific groups to provide customized views of the organization’s global address list”, with two notes from the same page: they “create only a virtual separation of users from a directory perspective, not a legal separation”, and implementing them “is a multi-step process that requires planning”. - The transport path. Mail between the two companies never leaves the server; it is internal mail. The organization-wide message size limits and the send connector are the same for both. ### When it does not work: where to look | What you see | Cause | Where it is described | | --- | --- | --- | | Collected mail for the new domain is refused with 550 5.7.1 Unable to relay | The domain is not an accepted domain in Exchange | Unable to relay guide | | Catch-all mail for the new domain ends up with the postmaster | The domain is missing under Accepted Recipient Domains in POPcon | Knowledge base | | Users of company B send with a company A address | The email address policy for company B does not match them or is evaluated after another policy | Section on email address policies above | | Company B’s outbound mail is rejected by the provider with Sender address is not allowed | All mail leaves through company A’s provider login | Provider smart host guide | | Mail to a colleague whose mailbox is still at the provider comes back as undeliverable | The domain is authoritative although not all its recipients are on the server | Section on partial domains above; knowledge base | ### Frequently asked questions ### Can one Exchange Server receive mail for several domains? Yes. Microsoft describes accepted domains as a global setting for the Exchange organization and states that you can have multiple accepted domains of the same or different types, and that an organization can be configured with multiple authoritative domains. Each domain whose mailboxes live on the server is added as an authoritative accepted domain; email address policies then give each group of users its address in the right domain. ### Does each company need its own send connector? A second send connector does not solve it. Exchange selects a send connector by the recipient's domain, its address space, and never by the sender, so two connectors with two smart hosts do not split the mail by company. With a relay that routes by sender, Exchange needs one send connector that hands all outbound mail to the relay; the relay then picks the provider and the login per sender domain. ### Do I need one POP3 or IMAP account per domain? You need at least one provider mailbox per domain that is collected, because each provider mailbox belongs to one domain. In POPcon every account is either a Single User account, delivered to one Exchange mailbox, or a Catch-All account, distributed by recipient address. For Catch-All accounts each domain must be listed under Accepted Recipient Domains, otherwise POPcon cannot tell which recipients are local. ### Can the users of company A see company B in the address book? By default yes: the companies share one Exchange organization and one global address list. Microsoft provides address book policies to give groups of users their own view of the address list, and notes that they create only a virtual separation of users from a directory perspective, not a legal separation. Implementing them is, in Microsoft's words, a multi-step process that requires planning. ### Which domain does Exchange use for its own postmaster address? The default domain. Microsoft states that one accepted domain is always configured as the default domain and that it is used in the external postmaster address, postmaster@. There is one default domain per organization, not one per company, so decide which company's domain it should be, typically an authoritative one. More in the Exchange mail flow guides , on the MultiSendcon and POPcon product pages, the MultiSendcon download page and the POPcon download page , or in the knowledge base . Auf Deutsch: Mehrere Firmen oder Domains auf einem Exchange Server . --- ## NDRs behind a POP3 connector: who tells the sender? Source: https://www.servolutions.com/guides/ndr-external-senders-pop3-connector Language: en Exchange mail flow guides › Authentication and SMTP errors ### NDRs for external senders behind a POP3 connector: unknown users, oversized mail, and providers that block empty senders When mail is collected from a provider mailbox, the provider has already accepted the message, so an external sender learns about an unknown recipient or a size rejection only if Exchange accepts the message from the connector and then generates a non-delivery report (NDR) — and if your outbound relay lets the empty MAIL FROM of that report through. A refusal during the SMTP session between the connector and Exchange reaches the connector and nobody else. A POP3/IMAP connector such as POPcon does not generate non-delivery reports itself. Updated on 2026-10-03 The Exchange behaviour on this page is taken from Microsoft Learn, where it is documented for Exchange Server 2016, 2019 and Subscription Edition; the connector side is taken from the POPcon and MultiSendcon knowledge base, whose articles on this subject were written for Exchange 2003 to 2013. Where the two differ, both are named. ### Why a non-delivery report is different behind a connector When a mail server on the internet delivers directly to Exchange, a refusal in the SMTP session goes back to the sending server, and that server informs its user. Behind a connector the sending server finished its work when the provider took the message. What happens afterwards is between three parties: the connector, which logs in to the provider mailbox and submits each message to Exchange over SMTP; Exchange, which either refuses the message in that session or accepts it; and the route by which Exchange sends its own mail out. A report for the original sender exists only if Exchange creates one, and it arrives only if that outbound route carries it. Microsoft describes the report itself in DSNs and NDRs in Exchange Server : “When there’s a problem delivering a message, Exchange sends an NDR to the message sender that indicates there was a problem.” For a recipient that does not exist the enhanced status code is 5.1.1, “RESOLVER.ADR.ExRecipNotFound; not found” or “User unknown”. ### The three cases | Case | If Exchange refuses in the SMTP session | If Exchange accepts the message | What the sender hears by default | | --- | --- | --- | --- | | Recipient does not exist | The message stays in POPcon’s queue ( knowledge base ) — unless POPcon re-routes unknown recipients to the postmaster, in which case it is delivered there | Exchange generates the non-delivery report, status 5.1.1 | Nothing in the first two variants; the report in the third | | Message is too large | Refused at the receive connector; POPcon moves it to its TOOLARGE folder | Refused by the organizational or mailbox limit; Exchange sends the non-delivery report | Nothing while the message waits in TOOLARGE; the report otherwise | | Recipient is out of office | Does not apply: the message is delivered | Exchange sends the automatic reply if the remote domain settings allow it | The reply, if it is allowed and the outbound relay accepts it | ### Unknown recipients: postmaster, queue or report This is the case with the most variants, because both the connector and Exchange have a setting for it. On the connector. POPcon version 3.00 and later has the option “Re-route email to unknown recipients” in the POP3/IMAP account configuration. When it is enabled, mail addressed to users who are not found in Exchange or Active Directory is redirected to the postmaster address set on the General configuration tab ( knowledge base ). The message reaches a person who can forward it; the sender is not told. How a connector finds the recipients of mail from a catch-all mailbox in the first place is described in Catch-all mailbox or one POP3 mailbox per user . In Exchange. If the option is off, POPcon submits the message to the address it was sent to, and Exchange decides. Microsoft’s description of accepted domains says an authoritative domain is one for which the Exchange organization “accepts messages that are addressed to recipients in these domains, and is responsible for generating non-delivery reports (also known as NDRs or bounce messages) for non-existent recipients” ( Accepted domains in Exchange Server ). Whether Exchange gets that far depends on recipient filtering. When the Recipient Filter agent is set to validate recipients, a message for a recipient that is not found is answered in the SMTP session: “the Exchange server sends a 550 5.1.1 User unknown SMTP session error to the sending server” ( Recipient filtering on Edge Transport servers ). Behind a connector the “sending server” is the connector, and the message stays in its queue. The knowledge base article How to have non-delivery reports sent for unknown users therefore gives two steps: disable “Re-route email to unknown recipients” in POPcon, and disable the blocking of unknown recipients in Exchange so that the message is accepted and answered with a report. It names the places for the older versions: - Exchange 2007 and 2010: Exchange Management Console › Organization Configuration › Hub Transport › Anti-Spam › Recipient Filtering : uncheck “Block messages sent to recipients that do not exist”. - Exchange 2003: Exchange System Manager › Global Settings › Message Delivery › Recipient Filtering : uncheck “Filter recipients who are not in the Directory”. In addition, “Allow non-delivery reports” must be checked under Global Settings › Internet Message Formats ( article with screenshots ). Exchange 2016, 2019 and SE. On these versions recipient filtering is managed in the Exchange Management Shell only, and Microsoft’s documentation points the other way from the older defaults. The parameter that makes the agent block “messages addressed to recipients that don’t exist in the organization” is RecipientValidationEnabled on Set-RecipientFilterConfig , and “the default setting is $false ”. For Mailbox servers Microsoft adds a warning: “Although the Recipient Filter agent is available on Mailbox servers, you shouldn’t configure it. When recipient filtering on a Mailbox server detects one invalid or blocked recipient in a message that contains other valid recipients, the message is rejected.” The agent is enabled when the antispam agents are installed on a Mailbox server, “but it isn’t configured to block any recipients” ( Recipient filtering procedures ). On a server where nobody changed this, Exchange accepts the message and the non-delivery report follows. On a server that was migrated or hardened over the years, read the state before assuming it: - Get-RecipientFilterConfig | Format-List Enabled,RecipientValidationEnabled shows whether the filter is on and whether it blocks recipients that do not exist (Microsoft’s own check is the same command with Enabled alone). - Get-AcceptedDomain | Format-List Name,AddressBookEnabled shows the setting per accepted domain: “By default, recipient filtering is enabled for authoritative domains, and disabled for internal relay domains and external relay domains.” - Set-RecipientFilterConfig -RecipientValidationEnabled $false switches the blocking of non-existent recipients off again. Microsoft’s warning about Mailbox servers has a practical side behind a connector: a message collected from a provider mailbox can carry several recipients of your domain, and one mistyped address among them should not cost the others their copy. ### Oversized messages The same split applies to size. A message that the receive connector refuses stays with POPcon in the TOOLARGE folder, and the sender hears nothing. To have the sender told, the knowledge base ( How to have NDRs sent for emails that are too large ) moves the decision behind the receive connector: set the connector’s limit high so that it does not refuse the message “at the wrong level”, and set the organizational maximum receive size to the limit you want. Exchange then accepts the message from the connector, finds it too large and sends the report itself. The limits, Microsoft’s default values and the commands are in Messages over 10 MB are not arriving . ### Out-of-office replies An automatic reply is not a non-delivery report, but it is the third message Exchange sends to external senders on its own, and it takes the same route. The knowledge base is clear about responsibility: this “is not a POPcon issue — it is an Exchange configuration setting” ( article ). For Exchange 2003 the switch is “Allow out of office responses” on the Advanced tab of the default entry under Global Settings › Internet Message Formats . On later versions the setting belongs to the remote domain and is changed with Set-RemoteDomain . Microsoft’s cmdlet reference lists three parameters that matter here: | Parameter | What it controls | Default per Microsoft | | --- | --- | --- | | AllowedOOFType | “the type of automatic replies or out-of-office (also known as OOF) notifications than can be sent to recipients in the remote domain”; valid values are External, ExternalLegacy, InternalLegacy and None | External: “Only automatic replies that are designated as external are sent” | | AutoReplyEnabled | “automatic replies from client email programs in your organization (for example, automatic reply messages that are generated by rules in Outlook)” | $false “for the built-in remote domain named Default in on-premises Exchange” | | NDREnabled | “whether to allow non-delivery reports (also known NDRs or bounce messages) from your organization to recipients in the remote domain” | $true | Read the current values with Get-RemoteDomain | Format-List Name,DomainName,AllowedOOFType,AutoReplyEnabled,NDREnabled . If a user’s external reply is configured in Outlook and still does not go out, either AllowedOOFType was set to None or InternalLegacy at some point, or the reply is generated and stopped on the way out — the next section. ### The way back: the empty sender and the outbound relay Non-delivery reports and automatic replies have one property in common: Exchange sends them with an empty envelope sender, an empty MAIL FROM , as the SMTP standard requires. They leave through the same send connector and the same smart host as every other message. If that smart host is a provider mailbox, the provider’s rules for senders apply to them too. IONOS is the documented case. Since January 2024 its outgoing mail servers refuse a message whose sender is not in the domain of the login mailbox, and a message with no sender at all, with Sender address is not allowed ; IONOS describes the change on its help page (German). The effect on Exchange is in our knowledge base ( IONOS blocks non-delivery reports and out-of-office messages ): the reports and replies are generated and then blocked by the provider, and “the behaviour is not configurable in Exchange or POPcon”. The fix is on the relay side. MultiSendcon , placed as an outgoing relay between Exchange and the provider, fills in a sender address for such messages: the address named in the message header where there is one, otherwise a fixed address configured for the account. The provider then accepts them. For a single provider login the lower-priced LITE edition is sufficient. The background, and the setup for several domains behind one provider, are in Using IONOS, Strato or GMX as the smart host for Exchange . A relay in the outbound path has its own setting for reports. MultiSendcon’s NDR Handling tab configures how non-delivery reports from the relay servers are handled and who receives them: back to the original sender, a designated postmaster address, or both. ### Postmaster or report: choosing per case | Arrangement | What happens to the message | Who knows | Settings | | --- | --- | --- | --- | | Re-route unknown recipients to the postmaster | Delivered to the postmaster mailbox | The postmaster; the sender is not told | POPcon: “Re-route email to unknown recipients” on, postmaster address set | | Non-delivery report for unknown recipients | Accepted by Exchange and not delivered | The sender, by the report | POPcon: re-routing off. Exchange: no blocking of non-existent recipients; NDREnabled true; outbound relay accepts the empty sender | | Report for the sender and a copy for the administrator | As above | Both | As above, plus Microsoft’s Set-TransportConfig -GenerateCopyOfDSNFor with the status codes to monitor and a mailbox assigned to the Exchange recipient ( Procedures for DSNs and NDRs ) | | Oversized mail kept for the administrator | Waits in TOOLARGE as a .msg file | Whoever looks into the folder or the log | Receive connector limit not higher than the organizational limit | | Oversized mail returned to the sender | Rejected by Exchange after acceptance | The sender, by the report | Receive connector limit high, organizational limit at the wanted size | The third row needs one remark from Microsoft’s page: “by default, no mailbox is assigned to the Exchange recipient, so any messages that are sent to the Exchange recipient are discarded.” Without that mailbox the copies go nowhere. ### When the sender hears nothing: where to look | What you see | Cause | Where it is described | | --- | --- | --- | | Mail for mistyped addresses arrives in the postmaster mailbox | POPcon re-routes unknown recipients | Knowledge base | | Mail for unknown addresses stays in POPcon’s queue | Exchange refuses the recipient in the SMTP session | Knowledge base , options A and B | | Large messages collect in TOOLARGE | Receive connector size limit | Size limits guide | | Exchange generates reports and automatic replies, external senders never receive them, the provider answers Sender address is not allowed | The provider refuses the empty sender | Provider smart host guide | | Out-of-office replies reach internal users only | Remote domain settings | Section above; knowledge base | The reply Exchange gave to the connector is in POPcon’s log, the file POPconSrv.log in the program directory; the codes are listed in the table of Exchange SMTP error codes . ### Frequently asked questions ### Can the POP3 connector send the non-delivery report itself? POPcon cannot. Its knowledge base states that POPcon cannot generate non-delivery reports itself and that this must be handled by Exchange; the German article adds the reason: to send anything back to the internet, POPcon would have to know the credentials of your provider's SMTP relay. The connector's part is to hand the message to Exchange in a way that lets Exchange produce the report. ### Why does mail to a mistyped address end up with the postmaster instead of bouncing? Because POPcon's option "Re-route email to unknown recipients" is switched on. With it, mail for an address that is not found in Exchange or Active Directory is redirected to the postmaster address from the General configuration tab. The message is not lost, but the sender is not told. To have a non-delivery report sent instead, switch the option off and let Exchange accept the message and answer it. ### Mail to unknown addresses stays in the connector's queue. What is wrong? Exchange is refusing the recipient during the SMTP session instead of accepting the message. Microsoft documents the reply of the Recipient Filter agent as 550 5.1.1 User unknown. A refusal at that point reaches only the connector, which cannot forward the message and keeps it in its queue. Either stop Exchange from blocking recipients that do not exist, so that it accepts the message and generates the report, or let POPcon re-route unknown recipients to the postmaster. ### Exchange generates the report, but the external sender never receives it. Why? A non-delivery report leaves Exchange with an empty envelope sender, and it leaves the same way as all other outbound mail. If the smart host is an IONOS mailbox, it is refused there: IONOS rejects messages with an empty sender since January 2024. Exchange has no setting that changes this. A relay between Exchange and the provider that fills in a sender address, such as MultiSendcon, makes the report acceptable. Also check that NDREnabled is still $true on the remote domain. ### Are out-of-office replies to external senders a connector setting? No. They are an Exchange setting on the remote domain and are not influenced by POPcon. Microsoft lists External as the default of the AllowedOOFType parameter, and for on-premises Exchange $false as the default of AutoReplyEnabled on the built-in remote domain named Default, which concerns automatic replies generated by rules in Outlook. Like non-delivery reports, the replies have an empty envelope sender and need a relay that accepts it. More in the Exchange mail flow guides , on the POPcon and MultiSendcon product pages, the POPcon download page and the MultiSendcon download page , or in the knowledge base . Auf Deutsch: Unzustellbarkeitsberichte hinter einem POP3-Connector . --- ## Microsoft 365 mailbox by IMAP with OAuth2 into Exchange Source: https://www.servolutions.com/guides/oauth2-pop3-imap-microsoft-365 Language: en Exchange mail flow guides › Authentication and SMTP errors ### Basic authentication is gone: fetching a Microsoft 365 mailbox by IMAP or POP3 with OAuth2 into Exchange Exchange Online no longer accepts a username and password for POP3 and IMAP; a connector that reads a Microsoft 365 mailbox must obtain an OAuth 2.0 token through a Microsoft sign-in and refresh it automatically, which is why “the password is correct but it keeps asking” is the symptom, not the problem. This guide explains what Microsoft switched off, what a service has to do instead, and the seven steps that connect a Microsoft 365 or Outlook.com mailbox to a POP3/IMAP connector for an on-premises Exchange Server. Updated on 2026-09-23 ### What Microsoft switched off Microsoft’s page Deprecation of Basic authentication in Exchange Online opens with the sentence that matters: Basic authentication is now disabled in all tenants, and nobody — neither the tenant administrator nor Microsoft support — can re-enable it. Basic authentication means the application sends a username and password with every request. Microsoft removed it for Exchange ActiveSync, POP, IMAP, Remote PowerShell, Exchange Web Services, the Offline Address Book, Autodiscover and Outlook for Windows and Mac, and disabled SMTP AUTH in every tenant where it was not in use. The cut-off for most cloud environments was 1 October 2022; after 31 December 2022 the switch could no longer be turned back on. | Protocol on Exchange Online | Username and password (Basic) | OAuth 2.0 (modern authentication) | Where Microsoft documents it | | --- | --- | --- | --- | | IMAP4 — outlook.office365.com, port 993, SSL/TLS | Refused in every tenant | Supported since 2020; the application presents a token | Deprecation page; POP3 and IMAP4 in Exchange Online | | POP3 — outlook.office365.com, port 995, SSL/TLS | Refused in every tenant | Supported since 2020 | same pages | | SMTP AUTH — smtp.office365.com, port 587, STARTTLS | Disabled where it was unused; Microsoft has announced the retirement of Basic authentication for SMTP AUTH | Supported since 2020 | Deprecation page | | App passwords | Do not help: the deprecation also prevents app passwords with apps that do not support two-step verification | — | Deprecation page | | Outlook as a POP3/IMAP client | Refused | Not available: Microsoft states there is no plan for Outlook clients to support OAuth for POP and IMAP; Outlook connects with MAPI/HTTP or EWS instead | Deprecation page; Can’t connect to Outlook by using POP/IMAP and Modern authentication | Two more details from the same Microsoft pages explain many support cases. If security defaults are enabled in the tenant, POP3 and IMAP4 are automatically disabled in Exchange Online, so even a correct OAuth2 setup logs in to nothing until an administrator enables the protocol for the mailbox. And the reason Microsoft gives for the whole change is worth repeating to whoever asks for the old way back: a stored password can be captured and reused against other services, while an OAuth access token has a limited lifetime and is specific to the application and resource it was issued for. ### What OAuth 2.0 means for a service that runs unattended A mail client with a person in front of it can sign in whenever Microsoft asks. A connector service that empties a mailbox every minute cannot, so the mechanism has to work without anyone watching. Microsoft’s developer page Authenticate an IMAP, POP or SMTP connection using OAuth describes the pieces: - The application is registered with Microsoft Entra — by the application’s developer, once. The registration is what the consent screen later names. POPcon ships as such a registered application; its version history for 4.10.0 describes the current form as a public-client app registration with PKCE and no client secret in the installer. - The user signs in once and consents. The application asks for a permission scope — for IMAP it is IMAP.AccessAsUser.All , for POP3 POP.AccessAsUser.All — and for offline_access . When the user approves that, Microsoft’s token endpoint issues a refresh token. - Refresh tokens are long-lived. Microsoft’s wording: the app can get new access tokens as older ones expire. That is the part that keeps a service running for months without a further sign-in. The connector stores the refresh token, not a password. - The token travels inside the protocol. The IMAP AUTHENTICATE XOAUTH2 command carries the user name and the access token in the SASL XOAUTH2 format instead of a password; POP3 uses AUTH XOAUTH2 . Nothing else about IMAP or POP3 changes: folders, message download and delete-after-download work as before. - Shared mailboxes are reached with a token obtained for a user who has access to them, with the shared mailbox’s address as the user name in the XOAUTH2 string — Microsoft documents this case on the same page. For the administrator this reduces to one practical rule: the sign-in happens in a browser on the machine where the connector runs, once per Microsoft account, with the account that owns the mailbox. After that the connector is on its own. ### Step by step: a Microsoft 365 mailbox in POPcon The steps below are the ones from the knowledge-base article Connect to Microsoft 365 or Outlook online accounts with OAuth2 , which also carries a screenshot of each screen. POPcon has supported OAuth 2.0 for Microsoft and Google accounts since version 4.8.1 (September 2024); the Microsoft flow was rebuilt in 4.10.0 (May 2026). - Set the account to IMAP on outlook.office365.com, port 993. In the connector's account settings choose IMAP as the server type, enter outlook.office365.com as the server and 993 as the port. Microsoft lists outlook.office365.com with port 993 and SSL/TLS as the IMAP4 setting for Exchange Online. - Select “OAuth2 Microsoft” as the authentication type. Leave the password field alone. With OAuth2 selected, the connector never sends a password to Microsoft. - Click “Connect OAuth2”. A Microsoft sign-in page opens in the browser on that machine. - Sign in with the mailbox account and complete MFA. Sign in as the Microsoft 365 user whose mailbox is to be fetched and complete the identity verification Microsoft requests, for example the Authenticator prompt. - Grant the connector permission to read the mailbox. Microsoft shows the permissions the application asks for; the consent page names the application “POPcon email forwarding”. Accept. - Check that the status reads “Authenticated”. Back in the connector the account status changes to Authenticated. The token is stored and refreshed by the connector from now on. - Run “Test access”. The test logs in to the mailbox with the token. If it passes, the account is ready and the schedule takes over. No password is entered at any point. The OAuth token is maintained and refreshed automatically by POPcon; the only thing that expires is the consent, and that survives the connector’s own service restarts and Windows updates. The walkthrough contains no step in which you register anything in your own tenant: the sign-in consents to POPcon’s registered application, which is why the consent page says “POPcon email forwarding” rather than the name of your organisation. ### Symptoms, and what each one really means | What you see | Cause | What to do | | --- | --- | --- | | Login fails although the password was just reset and is correct | Basic authentication is disabled tenant-wide; the password is never checked | Set the account to OAuth2 Microsoft and run Connect OAuth2 once. Do not create app passwords. | | OAuth2 sign-in succeeds, then the connector cannot open the mailbox | POP3/IMAP4 disabled for the mailbox or the tenant (security defaults, or the per-user setting) | An administrator enables IMAP4 (or POP3) for that mailbox in Exchange Online; Microsoft’s POP3 and IMAP4 page links the per-user procedure. | | The Microsoft consent page shows an error instead of the Accept button | The tenant restricts user consent to applications | An administrator grants the permission or adjusts User consent settings in Microsoft Entra ID. | | Accounts that worked for months ask for the sign-in again after a connector update | The application registration changed (POPcon 4.10.0) | Click Connect OAuth2 once per Microsoft account; nothing else to change. | | Outlook itself cannot be set up as a POP3/IMAP client for the same mailbox | Outlook has no OAuth for POP/IMAP, by Microsoft’s own statement | Not a connector problem. Outlook users connect with an Exchange profile; the connector keeps using IMAP with OAuth2. | ### IMAP or POP3 for a Microsoft 365 mailbox? Microsoft offers both, on the same host: IMAP4 on port 993 and POP3 on port 995, each with SSL/TLS, and OAuth 2.0 for each. The POPcon walkthrough for Microsoft 365 uses IMAP, and the knowledge-base article states that POP3 with OAuth2 is not available there for Microsoft accounts, so in practice the choice is made: IMAP on 993 with OAuth2 Microsoft . IMAP also has the property Microsoft describes for it — by default it does not remove downloaded messages from the server — which suits a connector that empties a mailbox on a schedule and, for a shared or migrated mailbox, may be asked to leave copies behind for a while. For Gmail and Google Workspace the same OAuth2 pattern applies with Google’s sign-in; the knowledge base has the Gmail walkthrough , and the guide Fetching Gmail and Google Workspace mail into Exchange over IMAP with OAuth2 explains what Google switched off and the eight steps. The general comparison of the two protocols for a connector — ports, implicit TLS versus STARTTLS, and the leave-on-server options — is in POP3 or IMAP for retrieving provider mailboxes into Exchange? . Both Microsoft 365 ports, 995 and 993, are implicit-TLS ports (“SSL/TLS” in Microsoft’s table): the connection is encrypted before the first command, and a client that sends STLS there is refused with -ERR Command is not valid in this state . The port and encryption pairs, with that error explained, are in POP3/IMAP over TLS for mail retrieval . Where the mailbox lives at a provider that still accepts a password — IONOS, Strato, GMX and most others — the account is set up with server type, port and password as described in How to download POP3 and IMAP mailboxes into Exchange Server 2016, 2019 and SE . Only the provider side of the connection changes with OAuth2; the delivery into Exchange over SMTP through the receive connector is the same for every account. ### Frequently asked questions ### Do I need an app password for the Microsoft 365 mailbox? No, and one would not work. Microsoft's deprecation page states that the removal of Basic authentication also prevents the use of app passwords with apps that do not support two-step verification. An app password is still a password sent with every request; Exchange Online no longer accepts that for IMAP and POP3. The connector authenticates with an OAuth 2.0 token instead, which it obtains through the Microsoft sign-in described above. ### Which server and port does the connector use? IMAP on outlook.office365.com, port 993, with SSL/TLS. That is the IMAP4 line in Microsoft's table of settings for Exchange Online. Microsoft also lists POP3 on the same host on port 995; the POPcon walkthrough for Microsoft 365 uses IMAP. ### The password is correct, but the connector keeps asking or fails to log in — why? Because the password is not the problem. Microsoft disabled Basic authentication for IMAP and POP3 in every tenant and nobody can re-enable it, so a username and password are refused no matter how correct they are. Switch the account to OAuth2 Microsoft and run the sign-in once. If the tenant has security defaults enabled, Microsoft additionally disables POP3 and IMAP4 in Exchange Online; an administrator then has to enable the protocol for that mailbox first. ### What if my tenant does not let users consent to applications? By default every user in a Microsoft 365 tenant may consent to an application that asks only for permissions that do not require administrator consent, and Microsoft's example of such a permission is access to the user's own mailbox. If your organisation has restricted user consent in Microsoft Entra ID, the consent step in the connector's sign-in is refused, and an administrator has to grant the permission, or relax the setting under Enterprise apps › Consent and permissions › User consent settings. ### Do existing accounts need to sign in again after a connector update? Sometimes. POPcon 4.10.0 changed the Microsoft OAuth mechanism to a public-client application with PKCE and no client secret in the installer, and its version history notes that existing Microsoft accounts had to re-authenticate once. After such an update, open each Microsoft account and click Connect OAuth2 again; the settings themselves are unchanged. More in the Exchange mail flow guides , on the POPcon product page , the download page or in the knowledge base . Auf Deutsch: Ohne Basic Authentication: Microsoft-365-Postfächer per IMAP mit OAuth2 nach Exchange holen . --- ## Choose the From address in Outlook on Exchange Server Source: https://www.servolutions.com/guides/outlook-choose-from-address-exchange Language: en Exchange mail flow guides › Sender address in Outlook ### How Outlook users can choose a different From address on Exchange on-premises: Send As, Send on Behalf, shared mailbox, add-in On an on-premises Exchange Server, Outlook sends from the primary SMTP address of the user’s mailbox unless the user has the Send As or Send on Behalf permission on another mailbox or group. Exchange Server has no setting that lets a user send from one of their own secondary addresses; the setting that does this, SendFromAliasEnabled , exists only in Exchange Online. That gap is why Outlook add-ins such as ChangeSender exist. Updated on 2026-09-21 ### What Exchange does without any extra configuration A mailbox can carry many e-mail addresses, but only one of them is the primary SMTP address. The others receive mail. When the user writes a message, Outlook offers the mailbox itself as the sender, and the recipient sees the primary address. Anything beyond that is a delegation. Microsoft documents the available permissions in Manage permissions for recipients (applies to Exchange 2016, 2019 and Subscription Edition): an administrator allows a user, the delegate, to send messages that appear to come from another mailbox or from a group. The important word is another. The permissions are granted on a separate recipient object, never on one of the user’s own additional addresses. The three terms are defined side by side in Send As vs Send on Behalf vs sending from an alias . ### The four ways, side by side | Way | Who sets it up, and where | What the recipient sees | Where replies go | | --- | --- | --- | --- | | Send As | Administrator, on the other mailbox or group: EAC → Recipients → the mailbox → Mailbox delegation, or Add-ADPermission . | The other mailbox or group. Microsoft: “There’s no indication that the message was sent by the delegate.” | To the other mailbox or group. | | Send on Behalf | Administrator, same place, or Set-Mailbox -GrantSendOnBehalfTo . | Both names: “ on behalf of ”. | To the mailbox or group, not to the delegate. | | A second or shared mailbox | Administrator creates the mailbox and assigns Full Access and Send As. Full Access alone opens the mailbox but does not allow sending from it. | The shared mailbox. | Into the shared mailbox, which every delegate has to watch. | | An Outlook add-in that sets the sender | Administrator installs a server component on Exchange and the add-in on the PCs; the user picks the address in the mail form. | The chosen address, without “on behalf of”. | To the chosen address, which is delivered wherever that address lives: the user’s own mailbox for an alias, a distribution group for a shared address. | The first three are built into Exchange and cost nothing but administration. They fit when the other sender really is a separate entity: the mailbox of a manager, a team mailbox, a group. They fit badly when one person simply has several addresses — a second domain after a merger, a role address such as sales@ next to the personal one — because each address then needs its own mailbox or group, and replies go to that object first instead of straight into the user’s mailbox. ### Granting Send As and Send on Behalf In the Exchange admin center open Recipients, select the mailbox the user should send as , click Edit and go to Mailbox delegation. For a group the page is called Group delegation. In the Exchange Management Shell Microsoft’s example for Send As is: Add-ADPermission -Identity "Helpdesk Support Team" -User Helpdesk -ExtendedRights "Send As" Send on Behalf is a property of the mailbox or group itself and is set with the GrantSendOnBehalfTo parameter of Set-Mailbox , Set-DistributionGroup or Set-DynamicDistributionGroup . To check who may send as a mailbox or group, replace the name and run: Get-ADPermission -Identity "Sales" | where {$_.ExtendedRights -like 'Send*'} | Format-Table -Auto User,Deny,ExtendedRights Three details from the same Microsoft page save a support call. If a user holds both permissions on the same object, Send As is always used. A delegate cannot send from a mailbox that is hidden from address lists. And Send As can be granted on distribution groups, dynamic distribution groups and mail-enabled security groups as well, which is the built-in answer when several people should write as info@ and no one needs a mailbox for it. ### Why a user cannot send from their own alias Exchange Online has an organization setting for exactly this. Microsoft’s reference for Set-OrganizationConfig describes SendFromAliasEnabled as the parameter that “allows mailbox users to send messages using aliases (proxy addresses)” and marks it as available only in the cloud-based service. Exchange Server 2016, 2019 and Subscription Edition have no equivalent setting. On premises the choice is therefore between turning each extra address into its own recipient object with Send As, and an add-in that sets the sender address of the individual message. ### One address for several people, several addresses for one person Two situations come up again and again in support. The first: two or more mailboxes should send from the same address, for example sales@company.com . Exchange does not share one sender address between mailboxes. With ChangeSender the shared address is added to each user’s sender list, and for the incoming side you create a distribution group with that address and add the people who should receive the replies. The steps are in the knowledge base article How to use the same sender address for two Exchange mailboxes . The second: one person answers for several addresses and wants everything in one inbox. Here the addresses stay ordinary secondary addresses of the mailbox, so nothing changes for incoming mail, and the add-in only changes what goes out. ### What the add-in route looks like with ChangeSender ChangeSender is an Outlook add-in with a server component for Exchange. It puts a send-as dropdown into the Outlook mail form, so the sender address is chosen per message. Around that choice it handles what otherwise goes wrong by hand: - Replies match. When a user replies, the sender address is set to the address the original message was received on. - Signatures follow. A signature named exactly like the sender address is switched in automatically when the address changes. - Sent items can be separated into different Outlook folders depending on the sender address used. - Keyboard shortcuts (CTRL-1, CTRL-2 and so on) select the most-used addresses. - Different defaults can be set for new messages and for replies. Both parts must be installed: the server component on the Exchange server and the add-in on every PC. The add-in alone looks as if it works, but the sender address does not change. ChangeSender supports Exchange 2000 through 2019 and Exchange Server SE with Outlook 2007 through the current Microsoft 365 Apps; a separate edition covers terminal servers and Citrix. The installation guide walks through both parts, and the download page has both installers. ### Keeping the choice under control Letting users pick a sender must not mean letting them pick any sender. The server installation of ChangeSender includes the utility “Configure ChangeSender Client Restrictions” with three settings per user: | Setting | What the user can choose | | --- | --- | | Default | The e-mail addresses configured for the user in Active Directory. | | Single address | One specific address, with no choice. | | Unrestricted | Any address, including shared addresses the user adds. | PCs in the Active Directory domain read these restrictions directly from Active Directory. For PCs outside the domain that reach Exchange over HTTPS, the utility exports a configuration file named after the user’s e-mail address, which is imported into the add-in on that PC. Details: How to restrict users’ choices for Send-As addresses in ChangeSender . ### Which way for which case - A colleague writes for a manager and that should be visible: Send on Behalf . - A team writes as support@ and works from a common inbox: a shared mailbox with Full Access and Send As. - Several people write as info@ , replies should reach all of them in their own inboxes: a distribution group with Send As, or the add-in with the shared address. - One person has several addresses or domains and wants one inbox, the right sender on every reply and the matching signature: the add-in . ### Frequently asked questions ### Can a user send from one of their own alias addresses on Exchange 2016 or 2019? Not with Exchange alone. A secondary SMTP address on a mailbox receives mail, but Outlook sends from the primary SMTP address. The organization setting that allows sending from aliases, SendFromAliasEnabled, is documented by Microsoft as available only in the cloud-based service. On Exchange Server you either make the address a separate mailbox or group and grant Send As, or you use an Outlook add-in such as ChangeSender that sets the sender address per message. ### What does the recipient see with Send As, and what with Send on Behalf? With Send As the message appears to come directly from the mailbox or group; Microsoft states that there is no indication that the message was sent by the delegate. With Send on Behalf the From line shows both, in the form Delegate on behalf of MailboxOrGroup. In both cases replies go to the mailbox or group, not to the delegate. If a user has both permissions on the same object, Send As is always used. ### A user has Full Access to a shared mailbox but cannot send from it. Why? Because Full Access does not include sending. Microsoft Learn describes Full Access as the permission to open the mailbox and to view, add and remove its contents, and adds that it does not allow the delegate to send messages from the mailbox. Assign Send As or Send on Behalf in addition. Also check that the mailbox is not hidden from address lists: a delegate cannot send from a hidden mailbox. ### Does ChangeSender need anything installed on the Exchange server? Yes. ChangeSender consists of a server component, installed on the Exchange server, and the Outlook add-in on each user's PC, and both must be installed. With the add-in alone ChangeSender appears to work, but the sender address does not change, because the Exchange-side processing is missing. Both installers are part of the download. More in the Exchange mail flow guides , on the ChangeSender product page or in the knowledge base . Auf Deutsch: Absenderadresse in Outlook wählen mit Exchange on-premises . --- ## POP3/IMAP over TLS: ports 995 and 993, STARTTLS, STLS error Source: https://www.servolutions.com/guides/pop3-imap-tls-ports-starttls Language: en Exchange mail flow guides › Inbound: POP3 and IMAP retrieval into Exchange ### POP3/IMAP over TLS for mail retrieval: ports 995 and 993, STARTTLS vs implicit TLS, and “-ERR Command is not valid in this state” POP3 and IMAP each have two ways to encrypt a connection: implicit TLS on a dedicated port — 995 for POP3, 993 for IMAP — where the connection is encrypted before the first command is sent, and STARTTLS (the POP3 command is spelled STLS ) on the plain port — 110 for POP3, 143 for IMAP — where the client connects in clear text and then asks the server to switch to encryption. The two must not be mixed: sending STLS on port 995 fails because the server expects TLS to be in place already, and a TLS handshake on port 110 meets a server that is waiting for plain text. Updated on 2026-10-06 The port and encryption facts on this page are taken from Microsoft Learn, where they are documented for Exchange Server 2016, 2019 and Subscription Edition and for Exchange Online; the connector side is taken from the POPcon help and knowledge base. Nothing here depends on a particular provider except where the provider’s documented settings are quoted. ### Two ways to encrypt the same protocol Microsoft describes the pair for Exchange Server in one sentence each: for POP3, “995 for always SSL/TLS encrypted connections, and 110 for unencrypted connections, or for opportunistic TLS (STARTTLS) that results in an encrypted connection after the initial plain text protocol handshake”; for IMAP4 the same with 993 and 143 ( POP3 and IMAP4 in Exchange Server ). “Always SSL/TLS” is what this page calls implicit TLS; “opportunistic TLS” is STARTTLS. The SMTP side that a connector or relay uses to submit mail has the same two shapes, which is why it is in the table. | Protocol | Plain port | Implicit TLS port (encrypted before the first command) | Upgrade command on the plain port | Documented by Microsoft | | --- | --- | --- | --- | --- | | POP3 | 110 | 995 | STLS | Exchange Server: 995 always encrypted, 110 plain or STARTTLS; Exchange Online: outlook.office365.com 995, SSL/TLS | | IMAP | 143 | 993 | STARTTLS | Exchange Server: 993 always encrypted, 143 plain or STARTTLS; Exchange Online: outlook.office365.com 993, SSL/TLS | | SMTP submission (the sending side of a mail program or relay) | 25 / 587 | 465 | STARTTLS | Exchange Online: smtp.office365.com 587, STARTTLS | The Exchange Online values are Microsoft’s table of settings in POP3 and IMAP4 in Exchange Online , where the encryption method is given as “SSL/TLS” for 995 and 993 and as “STARTTLS” for 587. The same page notes that security defaults disable POP3 and IMAP4 in a tenant and that disabling Basic authentication blocks both protocols — which is why a Microsoft 365 mailbox is fetched with OAuth 2.0, described in Basic authentication is gone: fetching a Microsoft 365 mailbox with OAuth2 . ### What the common servers expect | Mailbox at | POP3 | IMAP | Source | | --- | --- | --- | --- | | Microsoft 365 / Exchange Online | outlook.office365.com, 995, SSL/TLS (implicit) | outlook.office365.com, 993, SSL/TLS (implicit); the POPcon walkthrough uses IMAP, 993, OAuth2 Microsoft | Microsoft Learn (above); knowledge base | | Gmail / Google Workspace | pop.gmail.com, 995, server type POP3-SSL | imap.gmail.com, 993, OAuth2 Google | Knowledge base: Gmail by POP3 , Gmail with OAuth2 ; guide Gmail into Exchange with OAuth2 | | Another Exchange Server 2016, 2019 or SE (when you pull from a mailbox on a second Exchange) | 995 always encrypted; 110 plain or with STARTTLS | 993 always encrypted; 143 plain or with STARTTLS | Microsoft Learn, POP3 and IMAP4 in Exchange Server | | Other providers | Whatever the provider’s settings page lists for mail programs. “SSL/TLS” or “SSL” next to 995/993 means implicit TLS; “STARTTLS” next to 110/143 means the upgrade. The German knowledge base notes that 1&1, for example, only allows encrypted POP3 connections. | Knowledge base (German) | Two things follow for a connector. First, the TLS question is settled by the provider, not by the administrator: use the port the provider documents and the encryption mode that belongs to it. Second, for the two providers most mailboxes are at today, the documented combination is IMAP on 993 with implicit TLS and OAuth 2.0 — the choice between POP3 and IMAP itself is the subject of POP3 or IMAP for retrieving provider mailboxes into Exchange? . ### The classic misconfiguration: STLS on port 995 A thread on Microsoft Q&A shows the error exactly as it happens ( Unable to connect to POP email , a community question, not Microsoft documentation). The client’s log reads, in sequence: it opens a TLS connection to outlook.office365.com:995 ; the server answers +OK Microsoft Exchange POP3 server ready ; the client then writes STLS ; the server replies -ERR Command is not valid in this state. ; the client gives up with “Could not connect to POP3 server outlook.office365.com on port 995”. Everything up to the STLS line was correct. On port 995 the TLS handshake happens before the first POP3 command — that is what Microsoft means by “always SSL/TLS encrypted” — so by the time the client could send STLS , the session is already encrypted. There is nothing left to upgrade, and the server refuses the command as out of place; “not valid in this state” is the POP3 way of saying “not now”. The server is not broken and the password was never checked. The fix is on the client: select implicit TLS for port 995 (or 993), or, if the client is meant to use STLS , point it at port 110 (or 143) where the provider offers STARTTLS. The reverse mistake looks different. A client set to implicit TLS that connects to port 110 starts with a TLS handshake; the server is waiting for plain-text POP3 and does not answer in a way the client understands. There is no readable error line — the login fails or the connection times out before any mail is read. The symptom “timeout on a correct password” therefore points at the port and encryption pairing before it points at the provider. ### Setting it in the connector In POPcon the pairing is two fields on the account. The server type carries the default port — POP3 110, POP3-SSL 995, IMAP 143, IMAP-SSL 993 ( POP3/IMAP settings ) — and the encryption field has four values ( Account details ): | Encryption value | What it does | Belongs with | | --- | --- | --- | | TLS | Transport Layer Security, implicit — connects on the SSL port and encrypts before the first command | POP3-SSL / 995, IMAP-SSL / 993 | | SSL | Secure Sockets Layer, the legacy predecessor, also on the SSL port | 995 / 993 (legacy) | | STLS | StartTLS — connects in plain text on the standard port and upgrades to encrypted | POP3 / 110, IMAP / 143 | | SPA | Secure Password Authentication — an authentication option, not transport encryption | No port pairing of its own | The working combinations are TLS with 995 or 993 and STLS with 110 or 143. The Test access button checks the server connection, the authentication and the mailbox access in one go and is the quickest way to confirm the pairing; the timeout for a server response defaults to 180 seconds, so a wrong pairing can show up as a long wait rather than an instant error. POPcon supports TLS 1.2 and 1.3 and both variants, STARTTLS and implicit TLS, on POP3 (995) and IMAP (993). ### TLS versions The second thing that can be wrong with an encrypted connection is the protocol version. The POPcon version history lists TLS 1.2 support with version 4.0 (April 2021), and the product page states TLS 1.2 and 1.3 for the current version. The German knowledge base article on timeouts with Strato accounts describes the symptom of the old state: the 3.9x versions used an SSL/TLS library that had not been developed further for years and did not support TLS 1.2, and the article attributes the message “timeout while waiting for a response from the host” with Strato accounts to the slow TLS decryption of those versions. If a connector older than 4.0 suddenly cannot reach a provider on 995 or 993, the TLS version is the first suspect and the update is the fix. ### The SMTP side, for completeness A connector only retrieves over POP3 or IMAP; it hands mail to Exchange over SMTP, and a relay such as MultiSendcon sends outbound mail over SMTP to a provider. SMTP has the same two shapes: STARTTLS on port 587 (and 25) and implicit TLS on port 465. MultiSendcon supports both for every configured route; Microsoft documents smtp.office365.com on 587 with STARTTLS, and the SMTP account help notes that SSL is activated automatically when port 465 is used. Two knowledge-base articles are this page’s SMTP twins: “504 5.7.4 Unrecognized authentication type” appears when a server requires explicit TLS and the account’s SSL setting is not set to explicit SSL/TLS, and “530 5.7.0 Must issue a STARTTLS command first” is Exchange’s own SMTP side insisting on TLS before it accepts mail from the connector. The complete list of replies is in Exchange SMTP error codes explained . ### Symptoms and what each one means | Symptom | Cause | Fix | | --- | --- | --- | | Log shows STLS followed by -ERR Command is not valid in this state | STLS sent on an implicit-TLS port (995/993); the session was already encrypted | Set the encryption to TLS (implicit) for 995/993, or move STLS to 110/143 | | Login on 995 or 993 fails or times out although the password is correct; no readable server reply | Plain-text or STLS client on an implicit-TLS port, or implicit TLS selected on a plain port | Pair TLS with 995/993 and STLS with 110/143; run Test access | | Connection on 110 or 143 fails with TLS selected | The server expects plain text first | Select STLS, or switch to the SSL port with TLS | | Microsoft 365 mailbox refuses a correct password | Basic authentication for POP and IMAP is off in Exchange Online; not a TLS problem | IMAP, outlook.office365.com, 993, OAuth2 Microsoft — guide | | Google Workspace mailbox refuses a correct password | Google no longer accepts a username and password from a third-party app | IMAP, imap.gmail.com, 993, OAuth2 Google — guide | | Timeouts on an encrypted port with a POPcon 3.9x version | Old TLS library without TLS 1.2 | Update to the current version ( download ) | | 504 5.7.4 Unrecognized authentication type when MultiSendcon sends to Microsoft 365 | The server requires explicit TLS and the account is not set to it | Set the account’s SSL option to explicit SSL/TLS ( knowledge base ) | | 530 5.7.0 Must issue a STARTTLS command first from Exchange when the connector delivers | Exchange’s SMTP side is configured to require TLS before accepting mail | Knowledge base article ; the row in the SMTP error code table | The connection log that shows the exchange of commands is, for POPcon, the file POPconSrv.log in the program directory. How the retrieved mail then reaches Exchange — receive connector, accepted domain, first test — is in How to download POP3 and IMAP mailboxes into Exchange . ### Frequently asked questions ### Which port do I use for POP3 or IMAP over TLS? 995 for POP3 and 993 for IMAP when the connection is encrypted from the start (implicit TLS, which Microsoft calls SSL/TLS). The plain ports are 110 and 143; on those a client can upgrade to encryption with the STLS (POP3) or STARTTLS (IMAP) command where the server offers it. Microsoft documents exactly these pairs for Exchange Server 2016, 2019 and SE, and 995 and 993 with SSL/TLS on outlook.office365.com for Exchange Online. ### Can I send STLS on port 995? No. On port 995 the TLS handshake takes place before the first POP3 command, so the session is already encrypted when the client could send STLS. There is nothing left to upgrade and the server refuses the command; in the Microsoft Q&A case quoted on this page the reply was -ERR Command is not valid in this state. Choose implicit TLS for 995 and 993, or use STLS on port 110. ### What does "-ERR Command is not valid in this state" mean? It is a POP3 server's reply to a command that is not allowed at the current point of the session. After STLS it means the server will not negotiate an upgrade now, typically because the connection is already encrypted (port 995). The fix is in the client's encryption setting, not on the server. ### Which setting do I choose in POPcon for a Microsoft 365 or Gmail mailbox? The POPcon knowledge base uses IMAP on outlook.office365.com with port 993 and OAuth2 Microsoft for Microsoft 365, and IMAP on imap.gmail.com with port 993 and OAuth2 Google for Gmail. Both are implicit-TLS ports; the server type IMAP-SSL carries 993 as its default port. ### Which TLS versions does POPcon support? POPcon supports TLS 1.2 and TLS 1.3 and both variants, STARTTLS and implicit TLS, on POP3 (995) and IMAP (993). TLS 1.2 support arrived with version 4.0 in April 2021 according to the version history; the knowledge base attributes timeouts with Strato accounts to the old SSL/TLS library of the 3.9x versions, which did not support TLS 1.2. More in the Exchange mail flow guides , on the POPcon product page, the POPcon download page or in the knowledge base . Auf Deutsch: POP3/IMAP über TLS bei der Mailabholung . --- ## POP3 retrieval or MX record to Exchange: which to choose? Source: https://www.servolutions.com/guides/pop3-retrieval-vs-mx-record-exchange Language: en Exchange mail flow guides › Inbound: POP3 and IMAP retrieval into Exchange ### POP3 retrieval or MX record to Exchange: when a connector is the right choice and when it is not Pointing the MX record at your Exchange Server gives you direct SMTP delivery and is the better design when the server can be reached from the internet on port 25 under a name your public DNS can point to, and when you filter spam on arrival yourself; a POP3/IMAP connector is the right choice when one of those is missing or unwanted, during a migration, or when the provider mailboxes have to stay where they are. This guide sets the two designs side by side, says plainly when you do not need a connector, and describes the order in which shops usually move from one to the other. Updated on 2026-09-29 ### The two designs MX record to Exchange. Other mail servers look up the MX record of your domain and deliver to the host it names. Microsoft puts the requirement in one sentence in its post-installation guide ( Configure mail flow and client access on Exchange servers ): “To receive email from the internet for a domain, you need an MX resource record in your public DNS for that domain. Each MX record should resolve to the internet-facing server that receives email for your organization.” The example there pairs the MX record with an A record that carries the server’s public IP address. On the server, the default receive connector named “Default Frontend” listens for anonymous inbound SMTP mail on port 25, and Microsoft lists port 25/TCP from the internet (any) to the Mailbox server as the port required for inbound mail ( Network ports for clients and mail flow in Exchange ). POP3/IMAP retrieval. The MX record stays with the provider. The provider’s mail server accepts the mail and stores it in mailboxes; a connector service in your network logs in to each mailbox on a schedule, downloads what is new and submits it to Exchange over SMTP. POPcon is such a connector: a Windows service that downloads email from external POP3 and IMAP mailboxes into Microsoft Exchange Server and distributes it to the correct Exchange mailboxes. Exchange has no such function of its own; see Does Exchange Server have a built-in POP3 connector? ### Side by side | | MX record points at Exchange | POP3/IMAP connector | | --- | --- | --- | | Public DNS | MX record for the domain that resolves to your internet-facing server; in Microsoft’s example an A record with the public IP address behind it | Unchanged; the MX record stays with the provider | | Firewall, inbound | Port 25/TCP from the internet (any) to the Mailbox server, or to an Edge Transport server in the perimeter network | Nothing inbound from the internet | | Connections the design makes | Sending servers connect to you | The connector connects out to the provider (POP3 110/995, IMAP 143/993) and to Exchange on port 25 inside your network | | Spam filtering on arrival | Yours to provide: Edge Transport server, antispam agents enabled on the Mailbox server, or a filtering service in front | Whatever the provider applies to its mailboxes; POPcon PRO adds checks against real-time blacklists and antivirus scanning at the connector | | When Exchange is down | Mail waits on the sending servers, for as long as each of them keeps retrying | Mail waits in the provider mailbox; already downloaded messages wait in the connector and are retried every cycle | | Delay until the message is in the mailbox | None beyond SMTP delivery | Up to one retrieval interval; the minimum interval is 1 minute, 0 means continuous retrieval | | Finding the recipient | The SMTP envelope names the recipient | Exact with one provider mailbox per user; with a catch-all mailbox the connector reads the recipient from the message headers | | Accepted domain in Exchange | Required | Required | ### When the MX record is the better design If your server can take mail from the internet on port 25 and you have an answer for spam, direct delivery is simpler: one hop fewer, no retrieval interval, and the recipient is always the one the sender’s server named. A connector then adds nothing for that domain, and this guide does not suggest otherwise. The spam question deserves a closer look before the switch, because it is the part that the provider handled until now. Microsoft describes three places for it ( Antispam protection in Exchange Server ): - An Edge Transport server in the perimeter network. All antispam agents are installed and enabled there by default, and the Connection Filtering agent — the one that works with IP block lists and block list providers — is available only on Edge Transport servers. Microsoft describes the role as a way to minimise the exposure of the internal Exchange organization to threats on the internet. - Antispam agents on the Mailbox server. They have to be enabled first; Microsoft’s procedure does that with the script Install-AntiSpamAgents.ps1 ( Enable antispam functionality on Mailbox servers ). Microsoft’s own wording: you typically enable them if the organization has no Edge Transport server or does no other antispam filtering on incoming messages. The Malware agent, by contrast, is installed and enabled by default on Mailbox servers. - Filtering before the mail reaches Exchange — a mail gateway or a hosted filtering service that the MX record points at and that relays to Exchange. For Exchange this is SMTP delivery like any other, and no connector is involved. ### When a connector is the right choice - The server cannot, or should not, be reached from the internet on port 25. A connector needs no inbound opening at all: it makes outbound connections to the provider and delivers to Exchange inside the network. - The mailboxes have to stay at the provider. An address at the internet provider, a Gmail or Microsoft 365 mailbox, or a domain that remains hosted because webmail or other clients keep using it: there is no MX record of yours to change, or changing it would break the other users. The connector can leave the messages at the provider for a number of days so that those clients still see them. - Only part of a domain lives on your Exchange server. In a branch office that handles a subset of the company’s addresses the MX record belongs to the main office; the knowledge-base article Configuring POPcon for a branch office that handles only part of a domain describes that setup. - You are migrating. The connector brings the mail into the new Exchange server while DNS, firewall and filtering are still being prepared, and the switch of the MX record can follow later or never. - You want the provider to be the buffer. While Exchange is offline for maintenance, mail simply accumulates in the provider mailboxes and is collected afterwards (see the first question below). The price of the connector design is the one in the table: a retrieval interval instead of immediate delivery, provider mailboxes to maintain, and with a catch-all mailbox a dependency on the recipient headers the provider writes. Catch-all (multidrop) mailbox vs one POP3 mailbox per user explains that last point; the setup itself is in How to download POP3 and IMAP mailboxes into Exchange Server 2016, 2019 and SE . ### What happens while Exchange is down With a connector nothing is lost. POPcon delivers over SMTP, which requires an explicit acknowledgement for every message; until Exchange confirms receipt, POPcon keeps the message in a temporary .msg file and retries the delivery automatically on every following retrieval cycle ( Will I lose emails if Exchange is down when POPcon tries to deliver? ). Mail that has not been downloaded yet is still in the provider mailbox. With the MX record at Exchange, the message stays with the sending server, which tries again later. How long it keeps trying is decided by the sender, not by you. As an illustration of such a setting: Exchange Server, when it is the sending side, tries for a message expiration timeout of 2 days by default and then returns a non-delivery report to the sender ( Message retry, resubmit, and expiration intervals in Exchange Server ). Other mail systems have their own values. For a planned maintenance window this is rarely a problem; for a server that may be unreachable for days it is a reason to keep a buffer in front — a second Edge Transport server, a filtering service, or the provider mailbox. ### Moving from retrieval to the MX record Shops that start with a connector and later move the MX record usually do it in this order: - Run the connector first. Exchange receives the mail through the connector; set the accounts to leave messages on the server for a few days while the old clients are still in use. - Prepare Exchange for direct delivery. The domain must be an accepted domain ( Accepted domains in Exchange Server ); it already is if the connector delivers to addresses in that domain. Open port 25 from the internet to the server that is to receive the mail, and decide where spam is filtered. - Change the MX record in the public DNS of the domain so that it resolves to that server, and verify it with nslookup and set type=mx , as Microsoft’s guide describes. - Keep the connector running for a while. Anything that is still delivered to the provider mailboxes after the change is collected as before. When the provider mailboxes stay empty, remove the accounts from the connector. The outbound direction is not part of this change. Exchange sends through a send connector that either uses the MX records of the recipient domains ( Create a Send connector to send mail to the internet ) or routes everything through a smart host ( Create a Send connector to route outbound mail through a smart host ). If you send through provider smart hosts, the guide Multiple smart hosts in Exchange covers that side. ### Frequently asked questions ### Will I lose mail while Exchange is down? With a connector, no: the mail stays in the provider mailbox until it is collected, and a message that POPcon has already downloaded is kept as a .msg file until Exchange acknowledges it over SMTP; delivery is retried on every following retrieval cycle. With the MX record pointing at Exchange, the message waits on the sending server, and how long that server keeps trying is its own setting. Exchange itself, when it is the sender, gives up after a message expiration timeout of 2 days by default and returns a non-delivery report. ### Can I use both at the same time? Yes. The two are not exclusive, because every connector account is configured on its own. A domain whose MX record points at Exchange is delivered by SMTP, and mailboxes that remain at a provider - an ISP address, a Gmail or Microsoft 365 mailbox, a second domain that stays hosted - are collected by the connector. Both paths end at a receive connector of the same Exchange server. ### Does a POP3/IMAP connector need inbound ports opened on the firewall? No. The connector opens outbound connections to the provider (POP3 on 110 or 995, IMAP on 143 or 993) and hands the mail to Exchange over SMTP on port 25 inside your network. Direct delivery by MX record is the opposite: Microsoft lists port 25/TCP from the internet (any) to the Mailbox server as required for inbound mail. ### How do I check where the MX record of my domain points? Microsoft's verification step uses nslookup: open a command prompt, run nslookup.exe, change to a DNS server that can query your public DNS zone, type set type=mx and look up the domain. The value returned is the host that receives mail for the domain - your provider's mail server, a filtering service, or your own server. ### Does changing the MX record change how outbound mail is sent? No. The MX record decides where other servers deliver mail for your domain. Outbound mail leaves through a send connector, which either routes by the MX records of the recipient domains or hands everything to a smart host. The two directions are configured separately and can be changed independently. More in the Exchange mail flow guides , on the POPcon product page , the download page or in the knowledge base . Auf Deutsch: POP3-Abholung oder MX-Eintrag auf Exchange: wann ein Connector richtig ist – und wann nicht . --- ## POP3 or IMAP for pulling provider mail into Exchange? Source: https://www.servolutions.com/guides/pop3-vs-imap-for-exchange-retrieval Language: en Exchange mail flow guides › Inbound: POP3 and IMAP retrieval into Exchange ### POP3 or IMAP for retrieving provider mailboxes into Exchange? Ports, TLS, leave-on-server and OAuth2 For a connector that empties a provider mailbox into Exchange, POP3 and IMAP deliver the same messages; the choice is driven by what the provider allows (Microsoft 365 and Gmail take IMAP with OAuth2 for modern authentication), whether other clients also read the mailbox, and the TLS port conventions — 995 for POP3 over TLS, 993 for IMAP over TLS. This guide sets the two protocols side by side as a connector uses them, explains how the encryption setting and the port belong together, what happens to the copy at the provider, and which protocol the two large cloud providers effectively decide for you. Updated on 2026-09-25 ### What the two protocols do differently, and what a connector needs from them Microsoft’s own summary of the two protocols, written for mail clients, is a fair starting point ( POP3 and IMAP4 in Exchange Online ): by default POP3 clients remove downloaded messages from the server, though they can typically be configured to keep copies; POP3 downloads into a single folder and cannot synchronise several server folders; IMAP4 clients by default leave downloaded messages on the server and can create and access multiple folders there, and most of them can show senders and subjects before downloading a whole message. A connector that feeds an on-premises Exchange Server uses very little of that. It logs in to the provider mailbox on a schedule, downloads what is new, hands each message to Exchange over SMTP and then either deletes the copy at the provider or leaves it there. It does not build a folder tree, and Outlook users never see the provider mailbox at all — they see their Exchange mailbox. So the folder features that make IMAP attractive for a mail client hardly matter for a connector, and three other things matter more: - What the provider still lets you log in with. Microsoft 365 and Google no longer accept a username and password from an application for mailbox access; both need OAuth 2.0, and the two POPcon walkthroughs for them use IMAP on port 993. That decides the protocol before any other consideration. - Whether the mailbox has other readers. If a phone or a webmail user still reads the same provider mailbox, the messages must remain there for a while after the connector has taken its copy. Both protocols allow that in the connector; IMAP’s default behaviour, as Microsoft describes it, already matches that expectation. - The port and encryption combination the provider expects. This is where most first-connection failures come from, and it is the same question for both protocols. | | POP3 | IMAP | | --- | --- | --- | | Plain port | 110 | 143 | | Port over TLS | 995 (server type POP3-SSL) | 993 (server type IMAP-SSL) | | Encryption on the plain port | STLS (STARTTLS), upgrades the connection | STLS (STARTTLS), upgrades the connection | | Copy at the provider after download (Microsoft’s client default) | Removed | Left on the server | | Copy at the provider after download (in the connector) | Per account: delete, leave indefinitely, or leave N days | Per account: delete, leave indefinitely, or leave N days | | Folders on the server | One folder | Several; a connector reads the inbox | | OAuth 2.0 at Microsoft 365 in the POPcon walkthrough | Not available for Microsoft accounts, per the walkthrough | outlook.office365.com, 993, OAuth2 Microsoft | | OAuth 2.0 at Gmail / Google Workspace in the POPcon walkthrough | Legacy article only (pop.gmail.com, 995, password or app password) | imap.gmail.com, 993, OAuth2 Google | | Catch-all or single-user distribution, schedule, size of a download pass | Same account settings | Same account settings | ### Ports and encryption: the setting must match the port The four server types in the connector carry the four standard ports: POP3 on 110, POP3-SSL on 995, IMAP on 143 and IMAP-SSL on 993 ( POP3/IMAP configuration settings ). The encryption field on the account has four values, and two of them belong to a specific kind of port ( Account details ): - TLS — Transport Layer Security, implicit: the connection is encrypted from the first byte and is made on the SSL port, 995 or 993. - SSL — the legacy predecessor, also on the SSL port. - STLS — STARTTLS: the connection starts unencrypted on the plain port, 110 or 143, and is upgraded to encrypted. - SPA — Secure Password Authentication, an authentication option rather than transport encryption. The combinations that work are therefore TLS with 995 or 993 and STLS with 110 or 143 . A server that expects an implicit TLS handshake on 995 will not understand a client that opens the connection in plain text and then asks to upgrade, and a server that expects plain text on 110 will not understand a client that starts with a TLS handshake; in both cases the login fails or the connection times out before any mail is read. If a first connection to a provider fails, check this pairing before anything else. POPcon supports TLS 1.2 and 1.3 and both variants, STARTTLS and implicit TLS. What happens on the wire when the pairing is wrong — including the reply -ERR Command is not valid in this state after an STLS on port 995 — and what Microsoft documents for each port is in POP3/IMAP over TLS for mail retrieval: ports 995 and 993, STARTTLS vs implicit TLS . | Server type | Port | Encryption setting | | --- | --- | --- | | POP3-SSL | 995 | TLS (implicit) | | IMAP-SSL | 993 | TLS (implicit) | | POP3 | 110 | STLS (STARTTLS), where the provider offers it | | IMAP | 143 | STLS (STARTTLS), where the provider offers it | The Test access button on the account checks the server connection, the authentication and the mailbox access in one go; it is the quickest way to confirm the pairing, and the timeout for a server response defaults to 180 seconds. ### Leave on the server, or delete? Microsoft describes the client defaults — POP3 removes, IMAP4 leaves — but in a connector the behaviour is chosen per account and is the same for both server types ( delete / keep options ): - Delete emails from server — messages are removed immediately after a successful download. The provider mailbox stays empty; Exchange is the only copy. - Leave emails on server indefinitely — the connector never deletes. The connector tracks which messages it has already processed, so nothing is delivered to Exchange twice. - Leave emails on server for N days — messages stay for the given number of days and are then deleted. This is the window for other clients that also retrieve the same messages, and the usual setting during a migration, when the old client is still in use for a few days. Which one to choose has nothing to do with the protocol: if the connector is the only reader of the mailbox, delete after download keeps the provider mailbox from filling up; if a phone or webmail still reads it, leave the messages for as many days as that reader needs. With a catch-all mailbox for the whole domain the same setting applies to every recipient’s mail in that mailbox; the guide Catch-all (multidrop) mailbox vs one POP3 mailbox per user covers that choice. ### What the provider decides | Provider | Protocol, server, port | Authentication | Source | | --- | --- | --- | --- | | Microsoft 365 / Exchange Online | IMAP, outlook.office365.com, 993. Microsoft also documents POP3 on 995; the POPcon walkthrough uses IMAP and says POP3 with OAuth2 is not available there for Microsoft accounts. | OAuth2 Microsoft (Basic authentication for POP and IMAP is switched off) | Microsoft Learn ; KB walkthrough ; guide Basic authentication is gone | | Gmail / Google Workspace | IMAP, imap.gmail.com, 993. Google still documents POP on pop.gmail.com, 995; the POPcon OAuth2 walkthrough is written for IMAP. | OAuth2 Google (Workspace refuses a username and password from an app since 1 May 2025) | KB walkthrough ; guide Gmail into Exchange over IMAP with OAuth2 | | IONOS, Strato, GMX and other providers that accept a password | POP3-SSL on 995 or IMAP-SSL on 993, whichever the provider’s help page lists for mail programs; the exact host names and any provider-specific rules are not reproduced here. | Username and password ( Standard ) | The provider’s own settings page; setup steps in How to download POP3 and IMAP mailboxes into Exchange | Two rules fall out of the table. Where the provider requires OAuth 2.0, the walkthrough decides the protocol and it is IMAP over TLS on 993. Where the provider still takes a password, either server type works and the decision comes down to the leave-on-server question above; POP3-SSL on 995 is the conventional choice for a mailbox that the connector alone empties, IMAP-SSL on 993 for a mailbox that other clients keep reading. In both cases the encrypted port is the one to take — the plain ports exist for STARTTLS, not for unencrypted logins across the internet. ### Symptoms, and what each one really means | What you see | Cause | What to do | | --- | --- | --- | | The login fails or times out on port 995 or 993 although the password is correct | Encryption setting and port do not match: STLS selected on an SSL port, or TLS selected on a plain port | Set TLS with 995/993 or STLS with 110/143 and run Test access . | | A Microsoft 365 mailbox refuses the login with a correct password | Basic authentication for POP and IMAP is switched off in Exchange Online | Set the account to IMAP, outlook.office365.com, 993, authentication OAuth2 Microsoft ; see the Microsoft 365 guide . | | A Google Workspace mailbox refuses the login with a correct password | Google no longer accepts a username and password from a third-party app | Set the account to IMAP, imap.gmail.com, 993, authentication OAuth2 Google ; see the Gmail guide . | | Mail arrives in Exchange but stays in the provider mailbox as well | The account is set to leave messages on the server | Intended while other clients read the mailbox; otherwise switch the account to delete after download. | | Mail is downloaded correctly but never reaches Exchange | Not a POP3/IMAP question: the SMTP delivery into Exchange fails | Check the receive connector as in the setup guide and the article POPcon downloads email but cannot reach my Exchange server . | ### Frequently asked questions ### Which port do I use for POP3 or IMAP over TLS? 995 for POP3 over TLS and 993 for IMAP over TLS; the plain ports are 110 and 143. In the connector the server types POP3-SSL and IMAP-SSL default to 995 and 993. The encryption setting must match the port: TLS (implicit) connects on the SSL port, STLS (STARTTLS) starts on the plain port and upgrades the connection. ### Does the choice between POP3 and IMAP change anything on the Exchange side? No. The protocol is a setting of the provider account only. Delivery into Exchange runs over SMTP through the receive connector for every account, whichever protocol it uses; the accepted domain, the receive connector and the distribution rules are the same. The Exchange side is described in the guide How to download POP3 and IMAP mailboxes into Exchange Server 2016, 2019 and SE. ### Can I mix POP3 and IMAP accounts in one connector? Yes. Each account is configured with its own retrieval interval, protocol (POP3 or IMAP), credentials and distribution rules, so a Microsoft 365 mailbox over IMAP with OAuth2 and a provider mailbox over POP3-SSL with a password can run side by side in the same installation. ### Does Microsoft 365 still allow POP3? Microsoft documents both for Exchange Online: POP3 on outlook.office365.com port 995 and IMAP4 on port 993, each with SSL/TLS, and notes that security defaults disable both and that disabling Basic authentication blocks POP and IMAP. The POPcon walkthrough for Microsoft 365 uses IMAP on 993 with OAuth2 and states that POP3 with OAuth2 is not available there for Microsoft accounts, so for a Microsoft 365 mailbox the practical choice is IMAP. ### Do downloaded messages stay in the provider mailbox? That is a per-account setting in the connector, not a property of the protocol: delete after download, leave on the server indefinitely, or leave on the server for N days and then delete. When messages are left on the server, the connector tracks which ones it has already processed so they are not delivered twice. Microsoft describes the client defaults as POP3 removing downloaded messages and IMAP4 leaving them; the connector's setting decides in either case. More in the Exchange mail flow guides , on the POPcon product page , the download page or in the knowledge base . Auf Deutsch: POP3 oder IMAP für die Abholung von Provider-Postfächern nach Exchange? . --- ## SBS POP3 Connector: what it did and what replaces it Source: https://www.servolutions.com/guides/sbs-pop3-connector-replacement Language: en Exchange mail flow guides › Inbound: POP3 and IMAP retrieval ### The SBS 2008/2011 POP3 Connector: what it did, its limits, and the replacement for Exchange 2016 to SE The Windows SBS 2008 and 2011 POP3 Connector downloaded mail from external POP3 mailboxes and delivered it to an Exchange user or distribution group; Microsoft never shipped it for standalone Exchange, so shops that leave SBS need a separate connector service. This guide lists what the SBS connector did, where it stopped, how a current POP3/IMAP connector compares, and how to switch without losing a message. Updated on 2026-09-12 ### What the SBS POP3 Connector did Microsoft’s documentation for the Windows SBS 2008 POP3 Connector describes a small but complete feature. Each external POP3 mailbox was entered on the Accounts tab of the connector’s properties page in the Windows SBS Console and mapped to one SBS user account or one distribution group. The Scheduling tab set how often mail was retrieved, with a button to retrieve it immediately. The connector could connect over SSL and authenticate with Basic, SPA or APOP. It handed every downloaded message to Exchange over SMTP, so Exchange’s own antispam agent scanned it and moved spam to a badmail folder under the SBS data directory. Errors went to the Windows SBS event log. Two design decisions shaped a decade of small-business mail: replies to a message collected by POP3 were sent out through the local Exchange server, never back through the provider’s POP3 server; and messages larger than 10 MB were not retrieved at all, because the SMTP path into Exchange was limited to 10 MB. The connector logged an event and left the message at the provider for you to download or delete by hand. ### SBS POP3 Connector vs. a current POP3/IMAP connector The right-hand column describes POPcon , the connector service most SBS shops move to; the feature pages for POP3/IMAP accounts and scheduling hold the details. | | SBS 2008 / 2011 POP3 Connector | POPcon on Exchange 2013 to SE | | --- | --- | --- | | Mailbox mapping | One POP3 mailbox delivers to one SBS user or one distribution group | Single-user mailbox to one recipient, or catch-all mailbox split by the recipient headers, with accepted recipient domains and a re-route address for unresolved recipients | | Protocols | POP3 | POP3, POP3-SSL, IMAP and IMAP-SSL (default ports 110, 995, 143, 993) | | Encryption | SSL to the POP3 server where the provider supports it | TLS 1.2 / 1.3 on POP3 and IMAP connections | | Authentication | Basic, SPA, APOP | Password, plus OAuth 2.0 (modern authentication) for Microsoft 365 IMAP and Gmail mailboxes | | Messages over the Exchange size limit | Not downloaded; an event asks you to download or delete the message manually or raise the Exchange limit | Downloaded; if Exchange refuses the message it waits in the TOOLARGE folder and is resent through the PICKUP folder after the limit is raised, or Exchange sends the sender an NDR | | Retrieval schedule | Interval set on the Scheduling tab, or retrieve immediately | Fixed interval down to 1 minute, 0 for continuous retrieval, or exact times per weekday | | Spam and viruses | Exchange antispam agent after SMTP submission; spam to the badmail folder | Exchange still scans on receipt; POPcon PRO adds RBL blacklist checks and antivirus scanning before the message reaches Exchange | | Where it runs | On the SBS server only, managed in the Windows SBS Console | As a Windows service on Windows Server 2012 to 2025 or Windows 7 to 11, on the Exchange server or on a separate machine ( requirements ) | | Exchange versions served | The Exchange 2007 (SBS 2008) or Exchange 2010 (SBS 2011) inside the same SBS installation | Exchange 5.5 to 2019 and Exchange Server SE, all SBS editions, and other SMTP servers ( version list ) | | Mail left at the provider | Not documented on the Microsoft page | Delete after download, leave indefinitely, or leave for N days so another client can fetch the same mail | ### If you are still on SBS 2011, the connector is not the problem An honest reading of the table is that the SBS connector was adequate for its time: POP3 with SSL, a schedule, and delivery into Exchange. If your SBS 2011 server is still running and the mailboxes arrive, there is no reason to touch the connector today. The reason it gets replaced is that Small Business Server itself is retired: the next server is a regular Windows Server with Exchange 2016, 2019 or Exchange Server SE, and that Exchange has a POP3 service for clients but no connector, as explained in Does Exchange Server have a built-in POP3 connector? . The moment to plan the replacement is the moment you plan the migration off SBS, so that the new server collects mail from day one. The limits that did hurt in practice are the ones in the table: POP3 only, no IMAP; no OAuth 2.0, which Microsoft 365 and Gmail now expect instead of a plain password; messages over 10 MB stranded at the provider; and delivery to one user or one group per mailbox, which forced a distribution group wherever one provider mailbox served several people. A catch-all mailbox for the whole domain, the setup most small companies actually have at their provider, needs the header-based distribution that the SBS connector did not have. ### Replacing the connector when you leave SBS - Prepare the new Exchange server. Create a receive connector that accepts anonymous SMTP from the connector’s IP address and raise its 10 MB default message size; the steps are in Configuring Exchange 2013 / 2016 to receive mail from POPcon . This is the same preparation any SMTP source needs. - Install the connector. Download POPcon and install it on the new Exchange server or on any other Windows machine in the network. It runs as a Windows service and is configured with the POPcon Administrator program. - Re-enter the mailboxes. Take each entry from the SBS Accounts tab and add it as a POP3 or IMAP account in POPcon: server name, login, password, port, and the Exchange recipient for a single-user mailbox. A provider mailbox that receives mail for the whole domain becomes a catch-all account with your domain in the accepted recipient domains list. Enter the Exchange server name on the Exchange tab and a postmaster address on the General tab. - Keep a safety margin. For the first days set each account to leave mail on the server for a few days. If anything has to be rolled back, the messages are still at the provider. - Hand over. Stop the SBS POP3 Connector and start the POPcon service. Two connectors polling the same mailbox would each take a share of the mail, so the switch is a stop on one side and a start on the other, not a parallel run. Use Trigger mail retrieval in POPcon Administrator and watch the log window for the first cycle. - Later moves are a file copy. If POPcon ever has to move to another server, the configuration is one file, popcon.config , plus the UIDS_*.dat lists of already downloaded messages; see transferring the POPcon configuration to a new server . After the switch nothing changes for the users: mail keeps arriving in the same Exchange mailboxes, and replies still leave through the Exchange send connector, as they did under SBS. ### Frequently asked questions ### Is the SBS POP3 Connector available for Exchange 2016, 2019 or Exchange Server SE? No. The POP3 Connector was a component of the Windows Small Business Server console, and Microsoft never shipped it for standalone Exchange. Once the SBS server is retired, a separate connector service takes over: it downloads the provider mailboxes and submits the messages to Exchange over SMTP, which is the same way the SBS connector handed mail to Exchange. ### Can I keep the same provider mailboxes when I replace the connector? Yes. Nothing changes at the provider. The new connector logs in to the same POP3 or IMAP mailboxes with the same server name, login and password; only the machine that collects the mail changes. If you want a safety net during the switch, set the new connector to leave messages on the server for a number of days so that a rollback to the old connector still finds them. ### Why did the SBS POP3 Connector not download messages larger than 10 MB? Because it submitted mail to Exchange over SMTP and the SMTP path in SBS was limited to 10 MB; rather than download a message Exchange would refuse, the connector left it on the provider server and logged an event asking you to download or delete it manually or raise the Exchange limit. A current connector downloads the message and, if Exchange refuses it, keeps it in a TOOLARGE folder from which it is resent once the receive connector limit has been raised. ### Do I still need a distribution group to deliver one provider mailbox to several people? Not necessarily. The SBS connector delivered each POP3 mailbox to one user or one distribution group. With POPcon a single-user mailbox goes to one recipient, and a catch-all mailbox is split by reading the recipient headers of each message, so one provider mailbox for the whole domain reaches every Exchange user directly. Rules that forward, copy or reroute by sender, recipient, subject or attachment name are part of POPcon PRO. More on inbound mail flow in the Exchange mail flow guides , or in the knowledge base . Auf Deutsch: Der SBS-POP3-Connector: Funktionen, Grenzen und der Nachfolger . --- ## Send As vs Send on Behalf vs sending from an alias Source: https://www.servolutions.com/guides/send-as-vs-send-on-behalf-vs-alias Language: en Exchange mail flow guides › Sender address in Outlook ### Send As vs Send on Behalf vs sending from an alias in Exchange and Outlook Send As makes a message appear to come from another mailbox or group; Send on Behalf shows “A on behalf of B”; sending from an alias uses one of the same mailbox’s secondary addresses — a capability Exchange Online offers as a tenant setting and Exchange on-premises does not. The three are often mixed up in support requests because all three change what appears in the From line. They differ in who grants them, what the recipient sees, and where the reply ends up. Updated on 2026-09-22 ### The three terms, defined Send As and Send on Behalf are permissions. An administrator grants them on a mailbox or a group to another user, whom Microsoft calls the delegate. The definitions below follow Microsoft Learn, Manage permissions for recipients (Exchange Server 2016, 2019 and Subscription Edition); the Exchange Online page describes the same two permissions. - Send As allows the delegate to send messages as if they came directly from the mailbox or group. Microsoft: “There’s no indication that the message was sent by the delegate.” It does not allow the delegate to read the mailbox. - Send on Behalf allows the delegate to send messages from the mailbox or group, and the From address clearly shows that the delegate sent them: “ on behalf of ”. Replies go to the mailbox or group, not to the delegate. It does not allow the delegate to read the mailbox either. - Sending from an alias is not a permission at all. A mailbox has one primary SMTP address and can have further addresses, the aliases or proxy addresses. Sending from an alias means the From line carries one of those secondary addresses of the user’s own mailbox. A fourth term belongs in the same sentence because it is confused with the first two: Full Access lets the delegate open the mailbox and view, add and remove its contents. Microsoft adds that it does not allow the delegate to send messages from the mailbox. A shared mailbox therefore needs Full Access and Send As before anyone can write from it. ### Side by side | | Send As | Send on Behalf | Sending from an alias | | --- | --- | --- | --- | | What the recipient sees | The other mailbox or group. No indication of the delegate. | Both: “ on behalf of ”. | The alias address of the user’s own mailbox. | | Where it is granted | By the administrator on the other mailbox or group (EAC mailbox or group delegation, or Add-ADPermission ). | By the administrator on the other mailbox or group ( GrantSendOnBehalfTo ). | Nowhere per user. In Exchange Online it is the organization setting SendFromAliasEnabled ; the user then selects the alias in Outlook settings. | | Where replies land | In the other mailbox or group. | In the other mailbox or group, not with the delegate. | In the user’s own mailbox — the alias is one of its addresses. | | Exchange Server 2016, 2019, SE | Yes. | Yes. | No. Outgoing mail carries the primary SMTP address; there is no equivalent setting. | | Exchange Online | Yes. | Yes. | Yes, after the administrator enables SendFromAliasEnabled . Microsoft documents the From dropdown for Outlook on the web; compatible Outlook clients can send from and reply to aliases. | | Reads the other mailbox? | No. | No. | Not applicable — same mailbox. | Two rules from the same Microsoft page settle most edge cases. If a user has both Send As and Send on Behalf on the same mailbox or group, Send As is always used. And if the mailbox is hidden from address lists, the delegate cannot send from it with either permission. ### What an alias is, and why it is not a permission Microsoft’s administrator page Add another email alias for a user puts it plainly: the primary e-mail address is what typically appears in the From field when the user sends; the additional addresses of the same account are called aliases, and they receive mail. Nothing has to be granted, because the addresses belong to the user already. The question is only whether the server lets one of them appear as the sender. In Exchange Online that is decided by one setting. The reference for Set-OrganizationConfig describes SendFromAliasEnabled as the parameter that allows mailbox users to send messages using aliases (proxy addresses), and marks it as available only in the cloud-based service. Its default is $false : aliases on messages sent or received are rewritten to the primary e-mail address. With $true the rewriting stops, and compatible Outlook clients allow sending from aliases and replying to aliases. On the Microsoft 365 page the user-facing side is described for Outlook on the web: after the setting is enabled, each alias appears as a checkbox in the user’s Outlook settings, and a selected alias shows up in the From dropdown of the compose form. Exchange Server 2016, 2019 and Subscription Edition have no equivalent setting. On premises an alias receives mail and nothing more. That is the whole reason the question “how can my users send from their second address?” has a different answer on-premises than in the cloud. ### The reply trap Even where aliases can be used as senders, the reply is where the From line goes wrong. Microsoft’s alias page describes it for Microsoft 365: when a user answers a message that arrived at an alias, the From address depends on the client — Outlook on the web uses the alias at which the e-mail was received, Outlook desktop uses the primary address. The recipient of that reply then sees a different address than the one they wrote to, and a filter or a contact entry on their side stops matching. On Exchange Server the same thing happens with every alias, because there is no alias sending at all: whatever address the customer wrote to, the reply leaves with the primary address. An Outlook add-in that sets the sender per message fixes exactly this step. ChangeSender selects the sender address of a reply automatically, using the address the original message was received on, so the conversation keeps the address the customer knows. ### On Exchange Server: the choice is Send As or an add-in When one person has several addresses on premises, two routes remain. The first is built in: each extra address becomes its own recipient object, a mailbox or a distribution group, and the user gets Send As on it. The recipient sees that address, but replies land in the extra object, not in the user’s inbox. The second is an add-in that sets the sender address of the individual message while the address stays an ordinary alias of the mailbox, so replies arrive where they always did. How the built-in ways compare with a shared mailbox and with an add-in, including the commands to grant and verify the permissions, is in the guide How Outlook users can choose a different From address on Exchange on-premises . ### When you need an add-in, and what it does ChangeSender is an Outlook add-in with a server component for Exchange. It adds a send-as selection box to the Outlook mail form, so the From address is chosen per message from the addresses the user is allowed to use. Compared with the two permissions above: - The message does not show up as “sent on behalf of…”; the chosen address appears as “Any name” , configurable per address. - Several users can send from the same address, for example sales@company.com , without a mailbox or group being created for it. For the replies, a distribution group with that address collects them for everyone involved — the steps are in How to use the same sender address for two Exchange mailboxes . - Signatures change with the selected sender address, sent items can be filed into a folder per address, and keyboard shortcuts (CTRL-1, CTRL-2 and so on) pick the frequent addresses. - The administrator decides what each user may choose: the addresses from Active Directory (default), one fixed address, or any address. The utility is described in How to restrict users’ choices for Send-As addresses . Both parts must be installed — the server component on the Exchange server and the add-in on every PC; with the add-in alone the sender address does not change. ChangeSender works with Exchange 2000 through 2019 and Exchange Server SE and with Outlook 2007 through the current Microsoft 365 Apps. The installation guide covers both parts and the download page has both installers. ### Which term is the one you need - The recipient should see that a colleague wrote for someone else: Send on Behalf . - The message should look as if it came from a team mailbox or a group, with replies going there: Send As . - One person, several own addresses, replies in their own inbox, correct From on every answer: sending from an alias — a tenant setting in Exchange Online, an add-in on Exchange Server. ### Frequently asked questions ### Is an alias the same as Send As? No. Send As is a permission granted on another mailbox or group; the delegate sends messages that appear to come directly from that object. An alias is one of the additional e-mail addresses of the user's own mailbox. Exchange Server has no permission for sending from an alias: outgoing mail carries the primary SMTP address. Only Exchange Online has the organization setting SendFromAliasEnabled, and even there the default is off. ### Which one shows the real sender to the recipient? Only Send on Behalf. Microsoft documents its From line as "Delegate on behalf of MailboxOrGroup", so the recipient sees both names. With Send As there is no indication that the message was sent by the delegate. A message sent from an alias shows that alias, because it belongs to the same mailbox. ### Where do replies go? With Send As and Send on Behalf, replies go to the mailbox or group, not to the delegate; Microsoft states this explicitly for both permissions. A reply to a message sent from an alias arrives in the user's own mailbox, because the alias is one of its addresses. What the user's next reply then shows as From depends on the client: Microsoft notes that Outlook on the web uses the alias the message was received at, while Outlook desktop uses the primary address. ### How do users on Exchange Server pick a From address per message? Either the administrator turns each extra address into its own mailbox or group and grants Send As, or an Outlook add-in sets the sender address of the individual message. ChangeSender does the latter: a send-as dropdown in the Outlook mail form, the sender of a reply set to the address the original was received on, and no "on behalf of" in the result. It needs its server component on the Exchange server and the add-in on each PC. More in the Exchange mail flow guides , on the ChangeSender product page or in the knowledge base . Auf Deutsch: Senden als, Senden im Auftrag von oder von einem Alias senden . --- ## Where to install a POP3/IMAP connector for Exchange Source: https://www.servolutions.com/guides/where-to-install-pop3-connector Language: en Exchange mail flow guides › Inbound: POP3 and IMAP retrieval into Exchange ### Where to install a POP3/IMAP connector: on the Exchange server, a member server, or a workstation A POP3/IMAP connector needs two things from the network: outbound access to the provider’s POP3 or IMAP ports, and SMTP access to one receive connector of your Exchange Server. Nothing has to reach it from the internet. That is why it can run on the Exchange server itself, on any other Windows Server, or on a Windows 10/11 machine — POPcon is a Windows service and its requirements list Windows Server 2012 to 2025 and Windows 7 to 11. The placement decides which receive connector and which remote IP range you configure, which firewall the SMTP session on port 25 has to pass, and which antivirus exclusions you need. This guide sets the three placements side by side and lists the checks for the one symptom that placement causes: the connector downloads mail fine but cannot reach Exchange. Updated on 2026-09-30 ### What the connector needs, wherever it runs The requirements are the same at every placement; only the way to meet them differs. The figures come from the POPcon system requirements , the POP3/IMAP settings , the Exchange settings and the knowledge base. | Need | Detail | Where it is set | | --- | --- | --- | | Windows to run the service | Windows Server 2025, 2022, 2019, 2016, 2012 (incl. R2), Windows SBS 2011, or Windows 11, 10, 8, 7 (x86 or x64); no special CPU or memory requirements | Your choice of machine | | Outbound to the provider | POP3 on port 110 or 995 (TLS), IMAP on port 143 or 993 (TLS), or the port your provider names; the connection is always opened by the connector | Per account in POPcon; any firewall or proxy between the machine and the internet | | SMTP to Exchange | The Exchange server’s hostname or IP address (the help page gives exchange.local or 127.0.0.1 as examples) and the SMTP port, 25 by default | POPcon, Exchange Server settings; the receive connector on the Exchange side | | Disk space | 10 MB for the program plus the space to store downloaded messages temporarily until Exchange has accepted them | The POPcon program folder on the machine | | Network adapters | One adapter is sufficient; with two or more, POPcon lets you pick the adapter for external connections (to the provider) and the one for internal connections (to Exchange) | POPcon, Advanced options → Network configuration | | Administration | POPcon Administrator runs on the same machine or on any other machine on the network with access to the service, over TCP ports 22772–22774 | Windows firewall on the machine that runs the service | ### The three placements On the Exchange side, what matters is the receive connector. Microsoft describes the default receive connector Default Frontend on Exchange 2016, 2019 and SE as the one that “accepts anonymous connections from external SMTP servers” and calls it “the common messaging entry point into your Exchange organization”; it listens on port 25 on all available addresses and its remote IP ranges cover all IPv4 and IPv6 addresses ( Receive connectors in Exchange Server ). The same page defines the remote network settings of a receive connector as “the source IP addresses that the Receive connector listens to for connections”. So as long as nobody has narrowed those ranges, a connector on any machine in the network is inside them, and the one setting the Exchange 2013/2016 configuration guide adds is the Anonymous users permission group on that connector. The differences between the placements are elsewhere. | | On the Exchange server | On another Windows Server (member server) | On a Windows 10/11 workstation | | --- | --- | --- | --- | | Exchange server address in POPcon | The server’s own name or 127.0.0.1 | The Exchange server’s network name, not the internet domain name | Same as member server | | Path of the SMTP session on port 25 | Stays on the machine; no firewall in between | Windows firewall on the Exchange server and any network firewall between the two machines must allow port 25 from this machine | Same as member server; workstations are more often in a network segment that a firewall separates from the servers | | Receive connector | Default Frontend on port 25 with Anonymous users enabled; if its remote IP ranges have been narrowed, the address of the machine the connector runs on must be in them (all three placements) | | Antivirus exclusions | The POPcon program folder from real-time scanning, plus Microsoft’s exclusion list for Exchange servers (see below) | The POPcon program folder from real-time scanning | Same as member server; endpoint security products on workstations may also intercept outbound SMTP | | Availability of retrieval | As long as Exchange runs, the connector runs | As long as the server runs; Exchange can be restarted without stopping retrieval, the downloaded messages wait as files until Exchange accepts them | Only while the PC is on; mail waits at the provider in the meantime | | POPcon Administrator | Locally, or from another machine over ports 22772–22774 | Same | Same | | Proxy on the way to the internet | If outbound traffic leaves through a proxy, POPcon takes the proxy address and port for its POP3 and IMAP connections; a Microsoft ISA Server needs two outbound packet filters, remote port 110 (or 995) for POP3 and remote port 25 for SMTP (all three placements) | The middle column is the usual choice when the Exchange server is not supposed to carry anything but Exchange: the connector then behaves like any other application server that submits mail, and the Exchange side needs nothing beyond the anonymous permission on the receive connector. The left column is the simplest to set up because the SMTP session never leaves the machine; its price is that the Exchange server now also holds the antivirus and file-handling questions of the connector. The right column works, and the requirements say so, but the retrieval schedule then depends on a PC being on. ### Antivirus on the machine that runs the connector POPcon stores every downloaded message as a file in its program folder while it is being delivered to Exchange, and messages that Exchange rejects go to the TOOLARGE or BADMAIL subfolders, from where they can be moved to PICKUP for another attempt ( how to resend them ). A real-time virus scanner that deletes or quarantines such a file while POPcon works on it interferes with that; the knowledge base article POPcon hangs when my virus scanner deletes infected .msg files therefore recommends excluding the POPcon program folder (typically C:\Program Files (x86)\POPcon ) from real-time scanning and scheduling a periodic scan instead. Since version 2.8, POPcon sends a postmaster notification when a message file disappears unexpectedly rather than hanging. On the Exchange server itself the same class of problem exists for Exchange’s own files, and Microsoft has a page for it: Running Windows antivirus software on Exchange servers (applies to 2016, 2019 and SE). Its warning: “The biggest potential problem is that a program (such as antivirus) might lock or quarantine an open log or database file that Exchange needs to modify. This can cause severe Exchange Server issues, including potential data loss.” The page lists the folders, processes and file-name extensions to exclude from file-level and memory-resident scanning and notes that remote scanning can contribute to the same file locks. If you place the connector on the Exchange server, the POPcon folder is one more entry on a list you should already be maintaining. Two more notes on the same theme. Some endpoint security products intercept or block outbound SMTP; the knowledge base suggests disabling them temporarily to test when delivery to Exchange fails. And on POPcon PRO, whose antivirus engine scans the downloaded messages, Windows Data Execution Prevention can interfere with that engine; the fix in Windows Data Execution Prevention (DEP) is crashing the POPcon antivirus engine is to set DEP to “Turn on DEP for essential Windows programs and services only” on the machine that runs POPcon. ### “Downloads fine but cannot reach Exchange”: the checks This is the symptom that placement causes, and it appears almost only when the connector runs on a different machine than Exchange. The knowledge base article POPcon downloads email fine but cannot reach my Exchange server lists the checks in this order: - The Exchange server address. Use the server’s network name (for example exchangeserver ), not the internet domain name of your mail. The POPcon log file shows the IP address POPcon is actually trying to reach; verify it is the Exchange server’s. - The Exchange services. The Microsoft Exchange Transport service must be started on the Exchange server. - Network connectivity. ping exchangeserver from the POPcon machine. - SMTP port 25. telnet exchangeserver 25 from the POPcon machine must show the Exchange SMTP banner (a line starting with 220 ). If it does not, port 25 is blocked. - Firewalls. The Windows firewall on the Exchange server and any network firewall between the two machines must allow port 25 from the POPcon machine. - Endpoint security. Some antivirus or antispam products intercept outbound SMTP; disable them temporarily to test. - The receive connector. Verify that the POPcon machine’s IP address is within the allowed remote IP ranges of the receive connector (its Network tab). When the log shows “Could not reach Exchange SMTP server — check that IP port 25 is not blocked”, the article with that title gives the shorter version of the same list. What Exchange answers once the connection works, and what each reply means, is in Exchange SMTP error codes explained ; the full setup from accepted domain to first test is in How to download POP3 and IMAP mailboxes into Exchange 2016, 2019 and SE . ### Moving the connector to another machine The placement is not a decision for life. To move POPcon 4.x to another machine, install it there, stop the POPcon service, copy popcon.config and all UIDS_*.dat files from the old program folder into the new one, and start the service ( How can I transfer my POPcon configuration settings to a new server? ). The UIDS files are the lists of messages already downloaded from each mailbox; without them a mailbox set to “leave messages on the server” would be downloaded again. Alternatively, POPcon Administrator has File → Export Config and File → Import Config for the account settings. After the move, check the one Exchange-side setting the placement touches: if the receive connector’s remote IP ranges were narrowed to the old machine, they have to include the new one. If the standard installer cannot run on the target machine because of permission restrictions or Group Policy, the knowledge base describes an alternative installation method : install on a temporary machine, copy the program folder, run POPconSrv.exe there and choose Install and start service from its maintenance menu. ### Frequently asked questions ### Does the connector have to run on the Exchange server itself? No. POPcon runs as a Windows service on Windows Server 2012 to 2025 or on Windows 7 to 11, on the Exchange server or on any other Windows machine in the network. What changes with the placement is the path the SMTP delivery takes: from another machine the connector must reach Exchange on TCP port 25, and the receive connector that answers there must accept connections from that machine's address. ### Can I run it on a Windows 10 or Windows 11 PC? Yes. The POPcon requirements list Windows 11 and Windows 10 (x86 and x64) beside the server editions. The service runs for as long as the PC runs, so a PC that is switched off in the evening collects mail only during the day; the messages wait in the provider mailboxes in the meantime. For round-the-clock retrieval a server or an always-on machine is the better place. ### Which receive connector does the connector talk to? The one that listens on port 25 for anonymous SMTP connections. On Exchange 2016, 2019 and SE that is the receive connector "Default Frontend ", which Microsoft describes as accepting anonymous connections from external SMTP servers on port 25 from all IPv4 and IPv6 addresses. The Exchange configuration guide enables the "Anonymous users" permission group on it. If somebody has narrowed its remote IP ranges, the address of the machine the connector runs on has to be added; the knowledge base article on "Could not reach Exchange SMTP server" starts with exactly that check. ### Do I have to exclude anything from antivirus scanning? Exclude the POPcon program folder from real-time scanning wherever the connector runs: POPcon writes every downloaded message as a file and reads it back for delivery, and a real-time scanner that removes such a file interferes with that. Schedule a periodic scan of the folder instead. On the Exchange server itself Microsoft additionally lists the Exchange folders, processes and file types that a Windows antivirus program must not scan, because a locked or quarantined log or database file can cause severe problems including data loss. ### Can I administer the connector from my own desk? Yes. POPcon Administrator is a separate program that can run on any machine on the network with access to the POPcon service; it talks to the service over TCP ports 22772 to 22774 (the German knowledge base article also lists 22775). Open those ports in the Windows firewall of the machine that runs the service, and between the two machines if a firewall sits there. Closing the administrator does not stop the service. More in the Exchange mail flow guides , on the POPcon product page , the download page or in the knowledge base . Auf Deutsch: Wo installiert man einen POP3-/IMAP-Connector: auf dem Exchange-Server, einem Mitgliedsserver oder einem Arbeitsplatz-PC? --- ## MailSync Hub — Cloud IMAP Sync with OAuth | Servolutions Source: https://www.servolutions.com/mailsynchub Language: en Cloud SaaS · Azure-hosted New ### MailSync Hub Cloud IMAP Sync — OAuth 2.0 Ready Connect external IMAP mailboxes to Microsoft 365 or Exchange Online without installing anything on your servers. MailSync Hub runs in the cloud, authenticates using modern OAuth 2.0, and syncs email on a schedule — entirely managed by Servolutions. Contact Sales View Pricing No on-premise software OAuth 2.0 / Modern Auth Monthly or annual subscription The Problem ### When POPcon isn't the right fit POPcon is the right tool for on-premise Exchange environments. MailSync Hub is built for the growing number of organisations that have moved to Microsoft 365 or Exchange Online — where installing a Windows service isn't possible or desirable. ### On-Premise Exchange Use POPcon - Exchange 4.5 – 2019 + SE running on your servers - Full control of the server environment - Can install Windows services - One-time license, no recurring cost Learn about POPcon → or ### Microsoft 365 / Exchange Online Use MailSync Hub - Microsoft 365 or Exchange Online tenant - OAuth 2.0 / Modern Auth required - No server to install software on - Subscription-based, fully managed Get started → ### OAuth 2.0 Authentication Uses Microsoft's Modern Authentication standard. No stored passwords, no app passwords — just secure delegated access that complies with Microsoft's requirements for Exchange Online. ### Nothing to Install MailSync Hub runs entirely in our Azure infrastructure. No Windows service, no server agent, no maintenance. Set it up through a web portal and let it run. ### Scheduled Sync Configure sync intervals from minutes to hours. MailSync Hub polls the source IMAP mailbox on schedule and delivers messages to your 365 mailboxes automatically. ### Header-Based Distribution Same smart routing as POPcon: analyse message headers (To:, CC:, Delivered-To:) and deliver each email to the correct 365 mailbox automatically. ### Azure Infrastructure Hosted on Microsoft Azure for reliability and data residency. High-availability architecture with monitoring, logging, and automatic recovery built in. ### Simple Web Portal Configure and manage your sync accounts from a clean web interface. No technical setup required beyond authorising access to your Microsoft 365 tenant. Early Access ### MailSync Hub is launching We're opening MailSync Hub to early-access customers. Pricing is subscription-based, charged monthly or annually. Contact us to discuss your mailbox volume and get set up. Contact Sales View Pricing Azure-hosted 99.9% uptime SLA --- ## MultiSendcon — Multiple Send Connectors for Exchange Source: https://www.servolutions.com/multisendcon Language: en SMTP Routing · Exchange Add-on v3.3.1 ### MultiSendcon ™ Multiple Send Connectors for Exchange — Based on Sender Microsoft Exchange routes all outgoing mail through a single SMTP relay. MultiSendcon breaks that constraint: route each sender's outbound email through the correct relay server, with the right credentials — automatically. Download Free Trial Prices & Licensing 30-day full-featured trial Per-server license, one-time fee Exchange 4.5 – 2019 + SE supported When You Need It ### Common scenarios ### Multiple companies, one server You host Company A and Company B on the same Exchange. Each company uses a different mail provider. MultiSendcon routes each domain through the correct relay — automatically. ### Mix corporate and Google Workspace addresses Staff use both @company.com (Exchange) and @gmail.com (Google Workspace) addresses. MultiSendcon sends the Google addresses through Gmail's SMTP relay so authentication works correctly. ### IP reputation management Route high-volume bulk mail through a dedicated IP or provider while keeping transactional mail on your primary relay. Protect your main IP's sender reputation. Guide for the first scenario: Hosting several companies or domains on one Exchange Server — the Exchange settings per company and the relay account per sender domain. Capabilities ### What MultiSendcon does 01 Sender-Based SMTP Routing Routes each outgoing message to a different SMTP relay server based on who sent it. Configure unlimited routing rules — by sender email address, domain, or wildcard pattern. 02 Per-Sender Authentication Credentials Each routing rule carries its own SMTP relay login credentials. One sender can authenticate to Office 365, another to your ISP, a third to a dedicated transactional mail service — all from the same Exchange server. 03 TLS 1.2 / 1.3 Encryption All relay connections use TLS encryption. Supports STARTTLS and implicit TLS (port 465 / 587) for every configured outbound route. 04 Local IP Address Selection Bind outgoing connections to specific local network interface IP addresses per sender. Required when you need outgoing mail from different IPs for deliverability or compliance reasons. 05 Multi-Domain & Multi-Company Support Host multiple companies or domains on a single Exchange server and route each domain's outgoing mail through the correct relay — different provider, different credentials, fully isolated. 06 Recipient-Dependent Account Selection Route mail based on the recipient domain in addition to sender address. Useful when a specific destination requires a dedicated relay or authentication. 07 Exchange 4.5 – 2019 + SE Compatible Works with every version of Exchange Server ever released — through Exchange Server SE (Subscription Edition) — including all Small Business Server editions. No Exchange Online requirement. 08 MultiSendcon LITE Edition The LITE edition (single relay account, no per-sender routing) is available as a separate, lower-priced license. Useful for Exchange 2003 and earlier when SSL support for outbound SMTP is needed without the full multi-account feature set. Editions ### MultiSendcon vs MultiSendcon LITE Choose the edition that matches your environment. MultiSendcon Full Version Recommended - Unlimited routing rules by sender - Per-sender SMTP credentials - TLS 1.2 / 1.3 support - Local IP address selection per sender - Recipient-dependent routing - Multi-domain / multi-company support - 30-day free trial Download Free Trial View pricing → MultiSendcon LITE Single-Relay Edition Lower price - Single relay account - SSL / TLS support for outbound SMTP - Useful for Exchange 2003 and earlier - Multiple routing rules - Per-sender credentials - IP address selection Download LITE Trial Support & FAQ ### Common questions ### How does MultiSendcon decide which relay server to use? MultiSendcon intercepts outbound Exchange email before it leaves the server and matches the sender address against your configured routing rules. The first matching rule determines which SMTP relay server and credentials to use. Rules can match by exact address, domain, or wildcard pattern. ### Can I route email from different departments through different SMTP accounts? Yes. Configure one rule per department's sender domain or address pattern. For example: sales@company.com → Office365 SMTP, info@anotherdomain.com → Gmail SMTP. Each rule has its own credentials, TLS settings, and relay server address. ### Does MultiSendcon work with Office 365 or Google Workspace? Yes. Configure an SMTP account pointing to smtp.office365.com (port 587, STARTTLS) or smtp.gmail.com (port 587) with the appropriate credentials. Sender-address-based rules then route each email through the correct provider's relay. If you see "504 5.7.4 Unrecognized authentication type" with Office 365, see our Knowledge Base article on the connector configuration fix . ### What happens to emails that don't match any routing rule? Emails that don't match a specific rule fall through to the "Master Relay" configuration — a default SMTP relay used for all unmatched senders. You can also configure MultiSendcon to pass unmatched emails directly to Exchange's built-in send connectors. ### How do I install the Exchange Send Connector? The MultiSendcon installer can automatically create the Exchange Send Connector that routes outbound mail through MultiSendcon. If your environment requires manual setup (e.g., PowerShell remoting is disabled), see our Knowledge Base article "How to manually create the Send Connector in Exchange" . Why Exchange cannot select a send connector by sender on its own is explained in the guide Exchange send connectors route by recipient domain, not sender . ### What Exchange versions are supported? Exchange 2003 through Exchange 2019 and Exchange Server SE. MultiSendcon installs as a Windows service and integrates with Exchange's Send Connector framework — it does not require Exchange agents or transport pipeline plugins. ### The service won't start after I upgraded from an older version If the service fails to start and internals.log reports "ChilkatDotNet47.dll or one of its dependencies could not be found" , the server is missing the Microsoft Visual C++ 2015–2022 (x64) runtime that the current version requires. See Service won't start after upgrading for the one-step fix. Questions? Email support@servolutions.com — you'll reach the developers directly. All FAQ articles Installation Guide Release History ### Version history 2026 v3.3.1 June 23, 2026 Fixes a service-start failure after upgrading on servers that lack the Microsoft Visual C++ 2015–2022 (x64) runtime (Chilkat 11 / ChilkatDotNet47.dll). The installer now installs the runtime as a prerequisite, before the service starts. No configuration changes; existing settings are preserved. v3.3.0 May 23, 2026 New: Subject-based send-connector routing. Configure one or more keywords on each SMTP Relay Account; messages whose Subject header contains a matching keyword are routed via that account. Auto-substring matching by default; multi-keyword OR. v3.2.4 March 17, 2026 For out-of-office messages Exchange sends with empty SMTP envelope sender, MultiSendcon now replaces the empty sender with the MAIL FROM header field. v3.2.3 February 25, 2026 VC++ Library v14+ detection now works correctly. New SendConnector installation now works even with PowerShell remoting disabled. 2025 v3.2.2 December 12, 2025 VC++ Library detection improved for newer Windows Server installations. Admin/service communication no longer on a fixed address to avoid conflicts. v3.2.1 July 30, 2025 New SMTP component for improved TLS compatibility. New Administrator internals logfile with more diagnostic information. 2024 v3.2.0 December 18, 2024 Shows all recipients of a multi-recipient message instead of just the first. v3.1.9 December 07, 2024 Better error messages for multi-line SMTP server error responses. v3.1.7 July 24, 2024 Bugfix: Password encryption method incompatible with FIPS-compliant servers replaced with AES encryption. v3.1.1 June 12, 2024 Newest SMTP components fixing '220 2.0.0 SMTP server ready' error with Office 365. 2021 v2.98 May 23, 2021 TLS 1.2 and TLS 1.3 support. 2015–2016 v2.93 September 27, 2016 Correctly shows first line of multi-line SMTP error messages. v2.83 June 15, 2015 New: Replace SMTP envelope sender (MAIL FROM) with fixed sender email. v2.82 May 29, 2015 Passwords now stored encrypted (AES) in configuration file. v2.80 May 21, 2015 Emails to multiple recipients no longer split into individual emails. 2013–2014 v2.60 April 18, 2014 New: Multithreading for multiple simultaneous outgoing emails. v2.00 June 07, 2013 Automatically removes temporary X-MultiSendcon header fields before sending. v1.90 January 12, 2013 First public release. View full version history → ### Start your 30-day trial today Full-featured. No credit card. When you buy a license, just enter your key — no reinstallation needed. Download MultiSendcon View Pricing Ask a Question --- ## MultiSendcon Download v3.3.1 — Full & Lite Edition Source: https://www.servolutions.com/multisendcon/download Language: en ### Download MultiSendcon Current version: MultiSendcon v3.3.1 ### Editions - MultiSendcon (full version) — Download SetupMultiSendcon.exe - MultiSendcon LITE — single relay account; TLS 1.2+ support; for Exchange 2003 and earlier — Download SetupMultiSendconLite.exe ### Trial & Licensing Download, install, and test the full product free for 30 days without any restrictions. Purchase a license code to unlock unlimited use. ### Installation Note On some servers, the MultiSendcon installer might not be able to automatically add the Exchange Send Connector. If this occurs, manual configuration instructions are available in the support section . View full version history · Order license --- ## MultiSendcon Administrator Utility Source: https://www.servolutions.com/multisendcon/help/admin Language: en ### MultiSendcon Administrator The MultiSendcon Administrator is the configuration and monitoring utility. The main MultiSendcon service runs as a Windows background service; the Administrator is a separate application for managing it. ### What it does - Shows a real-time scrolling log of MultiSendcon activity - Provides access to all configuration tabs (Master Relay, Relay Servers, NDR Handling, License, Advanced) - Allows you to test SMTP accounts ### Service independence The MultiSendcon service continues running when the Administrator is closed. You only need the Administrator open for monitoring or configuration changes. ### Stop log update Click Stop log update to pause the real-time log display. This allows you to read or copy log entries during periods of high activity without the display scrolling. The service continues operating normally. Configuration tabs: Master Relay · Relay Servers · NDR Handling · License · Advanced --- ## MultiSendcon — Advanced Configuration Source: https://www.servolutions.com/multisendcon/help/config-advanced Language: en ### Advanced Configuration These settings are not needed in most deployments. Start with the defaults and only change them if instructed by Servolutions support. ### Concurrent Sending Threads Limits the number of simultaneous outgoing SMTP connections MultiSendcon makes when processing a queue of messages. Useful if your email provider restricts the number of concurrent connections from a single IP address. ### Archiving When enabled, MultiSendcon writes a copy of each outgoing email to a file on disk. This is a diagnostic feature — only enable it when requested by Servolutions support to troubleshoot a specific issue. Disable it afterwards to avoid filling up disk space. --- ## MultiSendcon — License Source: https://www.servolutions.com/multisendcon/help/config-license Language: en ### License MultiSendcon starts as a free 30-day trial . All features are available during the trial with no restrictions. After purchasing a license from the web shop , enter the license code on this tab. The license is applied immediately — no reinstallation or reconfiguration is required. --- ## MultiSendcon — Master Relay Configuration Source: https://www.servolutions.com/multisendcon/help/config-master-relay Language: en ### Master Relay Configuration The Master Relay is the local SMTP endpoint that Exchange sends outgoing emails to. MultiSendcon listens here and routes messages to the appropriate relay server based on the sender address. ### Local IP Address The IP address where MultiSendcon binds and listens for incoming SMTP connections from Exchange. The Exchange send connector must point to this address. On systems with multiple network cards, select the appropriate one. ### IP Port Standard SMTP uses port 25, but Exchange already uses port 25 on its receive connectors. MultiSendcon must use a different port — the default is 2500 . Any unused port will work. The Exchange send connector must be configured to use this same port number. ### Access Restrictions You can restrict which IP addresses are allowed to connect to MultiSendcon. Best practice is to limit access to only the Exchange server’s IP address, preventing MultiSendcon from being misused as an open relay by other systems. Next: Relay Servers → | Installation Guide --- ## MultiSendcon — NDR Handling Configuration Source: https://www.servolutions.com/multisendcon/help/config-ndr-handling Language: en ### NDR Handling Configuration Non-Delivery Reports (NDRs) are generated when an email cannot be delivered. This tab configures how MultiSendcon handles NDRs from relay servers. ### NDR Recipient - Back to sender — routes the NDR to the original message sender - To postmaster — sends the NDR to a designated postmaster address instead - To both sender and postmaster — sends the NDR to both parties ### Exchange Server Settings MultiSendcon needs to know where to send the NDR messages it generates. Configure: - Exchange server name - SMTP port (typically 25) - Authentication credentials (usually not required for internal Exchange delivery) ### NDR Source Address The email address that appears as the sender on NDR messages. Use an administrator’s address here so that if a recipient replies to the NDR, it reaches someone who can help. Next: License → --- ## MultiSendcon — Relay Servers Configuration Source: https://www.servolutions.com/multisendcon/help/config-relay-servers Language: en ### Relay Servers Configuration This tab defines the SMTP accounts and direct DNS delivery options that MultiSendcon uses to route outgoing email. The key feature is sender-based routing : each account can be assigned a sender address range (domain), so different senders use different outgoing relay servers. ### Add Relay Server Adds a standard SMTP relay account. Configure: - SMTP server address and credentials - Sender mask — which sender domains use this account (e.g. *@company.com or user@company.com ) - See SMTP Account settings for full details ### Add Direct DNS Delivers email directly to the recipient’s mail server via DNS MX lookup, without using a third-party relay. Useful as a fallback for addresses not matched by any relay account. See Direct DNS settings . ### Priority Order When multiple accounts match a sender address, the topmost entry in the list takes priority. Use the Up/Down buttons to set the priority order. Accounts with the same sender mask are tried in list order. This allows primary/fallback relay configurations. Next: NDR Handling → --- ## MultiSendcon — SMTP Account Settings Source: https://www.servolutions.com/multisendcon/help/smtp-account Language: en ### SMTP Account Settings Configure a relay server account. MultiSendcon routes outgoing emails through this account for senders matching the configured sender mask. ### Basic Settings - Descriptive Name — a label to identify this account in the account list - SMTP Server — your provider’s relay server address (e.g. smtp.yourprovider.com ) - Username / Password — authentication credentials for the relay server - IP Port — typically 25, 587, or 465. SSL is activated automatically when port 465 is used ### Network Options - Local IP Address — on systems with multiple network cards, select which card handles this account - HELO/EHLO Domain — the domain name used in the SMTP HELO or EHLO command when signing on to the relay server ### Performance & Routing - Minimum Wait — seconds between consecutive emails sent through this account. Set to 0 for maximum throughput. Increase if the provider enforces a rate limit - Sender Address Filter — restricts this account to specific sender addresses. Use *@domain.com for all senders in a domain, or user@domain.com for a single user. Leave blank to match all senders - Recipient Address Filter — restricts this account to specific recipient addresses (same format as sender filter) ### Fixed Sender Address Replacement (v2.50+) Replaces the outgoing sender address with a fixed address. Useful when a relay provider requires a specific sender address (e.g. the authenticated account address). Private email override: Users can mark a message as “Private” (via the Sensitivity field in Outlook) to bypass sender replacement for that message. Test this account → --- ## MultiSendcon — Direct DNS / Direct Send Settings Source: https://www.servolutions.com/multisendcon/help/smtp-account-direct Language: en ### Direct DNS (Direct Send) Settings Direct DNS delivery sends email directly to the recipient’s mail server via DNS MX lookup, without using a third-party SMTP relay. Suitable for servers with a fixed, routable IP address that is listed in DNS. ### Settings - Descriptive Name — identifies this entry in the account list - Local IP Address — the outgoing IP address for direct sends. On multi-NIC systems, select the appropriate network card - HELO/EHLO Domain — the domain name announced during the SMTP handshake - Minimum Wait — seconds between consecutive emails. Set to 0 for maximum speed - Sender Address Filter — which senders use this direct delivery method ( *@domain.com or blank for all) - Recipient Address Filter — which recipients this entry handles - Sender Address Replacement — replace the sender address with a fixed value (v2.50+) Direct DNS is often added as a low-priority fallback entry at the bottom of the relay servers list, so that messages not matched by any relay account are still delivered. --- ## MultiSendcon — Test SMTP Account Source: https://www.servolutions.com/multisendcon/help/test-smtp-account Language: en ### Test SMTP Account Use this dialog to verify that a configured relay server account is working correctly before relying on it for live email. ### Fields - From — the sender address for the test message. Choose an address that matches the sender filter configured for this account, so the correct relay is selected - To — the recipient address that will receive the test message Click Send to send a test email through the selected SMTP account. Check the MultiSendcon Administrator log to confirm the message was accepted and relayed successfully. --- ## MultiSendcon Version History — Release Notes Source: https://www.servolutions.com/multisendcon/history Language: en ### MultiSendcon Version History ### 2026 v3.3.1 (June 23, 2026) — Fixes a service-start failure after upgrading on servers that lack the Microsoft Visual C++ 2015–2022 (x64) runtime (Chilkat 11 / ChilkatDotNet47.dll ). The installer now installs the runtime as a prerequisite, before the service starts. No configuration changes; existing settings are preserved. v3.3.0 (May 23, 2026) — New: Subject-based send-connector routing. Configure one or more keywords on each SMTP Relay Account; messages whose Subject: header contains a matching keyword are routed via that account. Auto-substring matching by default (typing invoice matches any subject containing ‘invoice’); explicit *foo* glob also supported. Multiple keywords are OR-combined. v3.2.4 (March 17, 2026) — For out-of-office messages Exchange sends with empty SMTP envelope sender, MultiSendcon now replaces the empty sender with the MAIL FROM header field. v3.2.3 (February 25, 2026) — Detection of VC++ Library v14+ now works correctly. Installation of new SendConnector in Exchange now works even with PowerShell remoting disabled. ### 2025 v3.2.2 (December 12, 2025) — VC++ Library detection improved for newer Windows Server installations. Admin/service communication no longer on a fixed address to avoid conflicts. v3.2.1 (July 30, 2025) — New SMTP component for improved TLS compatibility. New Administrator internals logfile with more diagnostic information. ### 2024 v3.2.0 (December 18, 2024) — Shows all recipients of a multi-recipient message instead of just the first. v3.1.9 (December 07, 2024) — Better error messages for multi-line SMTP server error responses. v3.1.8 (August 12, 2024) — Removed forced VC++ Redist installation; added warning in Admin if libraries are missing. v3.1.7 (July 24, 2024) — Bugfix: Password encryption method incompatible with FIPS-compliant servers replaced with AES encryption. v3.1.6 (July 17, 2024) — More secure Exchange Sendconnector setup. v3.1.5 (July 15, 2024) — Added installer for VC++ redist with UI. v3.1.4 (July 12, 2024) — Extended log file for Exchange send connector configuration installer. v3.1.3 (July 12, 2024) — Auto-installs missing VC++ Redist. v3.1.1 (June 12, 2024) — Newest SMTP components fixing ‘220 2.0.0 SMTP server ready’ error with Office 365. ### 2021 v2.98 (May 23, 2021) — TLS 1.2 and TLS 1.3 support. ### 2016 v2.93 (September 27, 2016) — Correctly shows first line of multi-line SMTP error messages. v2.92 (July 12, 2016) — Detection of accessible local IPs improved. v2.91 (April 19, 2016) — Error handling for extremely large emails. ### 2015 v2.90 (December 14, 2015) — Email addresses with name part ending in minus sign now accepted. v2.83 (June 15, 2015) — New: Replace SMTP envelope sender (MAIL FROM) with fixed sender email. v2.82 (May 29, 2015) — Passwords now stored encrypted (AES) in configuration file. v2.80 (May 21, 2015) — Emails to multiple recipients no longer split into individual emails. v2.76 (March 13, 2015) — SMTP timeout configurable per account. v2.74 (February 25, 2015) — Better error messages for oversized NDRs. Daily log file options. 45x temporary error code retry fix. v2.71 (January 14, 2015) — New ‘advanced’ page with configurable concurrent sending threads limit. ### 2014 v2.69 (December 17, 2014) — Improved SSL on port 465. Special handling of ‘421 invalid sender domain’ and ‘421 Too much load’ errors. v2.64 (August 14, 2014) — New: Default sender address for emails with empty sender spec <>. v2.60 (April 18, 2014) — New: Multithreading for multiple simultaneous outgoing emails. v2.52 (March 28, 2014) — Configurable email address for NDRs. v2.50 (March 05, 2014) — New: Replacement of sender addresses with a fixed sender address. ### 2013 v2.00 (June 07, 2013) — Automatically removes temporary X-MultiSendcon header fields before sending. v1.90 (January 12, 2013) — First public release. --- ## Install MultiSendcon — Setup Guide for Exchange Source: https://www.servolutions.com/multisendcon/install Language: en ← MultiSendcon ### How to install MultiSendcon MultiSendcon installs as a Windows service that automatically starts when the server boots and runs in the background. We designed MultiSendcon to work as a SMTP relay server that accepts emails from Exchange via SMTP on an alternative IP port (Exchange thinks of MultiSendcon as a simple Smarthost) and distributes those emails to different SMTP accounts and other relay servers out on the internet. These are the necessary steps to install and configure MultiSendcon: - Download and run the SetupMultiSendcon Installer - Configure MultiSendcon options and SMTP accounts - Update the MultiSendcon Send Connector in Exchange to connect to your new MultiSendcon ### 1. Download and run the SetupMultiSendcon Installer You can find the installer on our download page . The installation software will install and start the MultiSendcon background service and the MultiSendcon Administrator and will also add a new send connector to your Exchange. Don’t worry – for the moment all outgoing emails will still go through your usual send connectors because the new MultiSendcon send connector is created disabled. You will enable it after configuring MultiSendcon in the last step. Attention: On some servers, the MultiSendcon installer might not be able to automatically add the Exchange Send Connector that connects to it. Here is how to do it manually . ### 2. Configure MultiSendcon options and SMTP accounts MultiSendcon installs with its own Administration utility. Please start MultiSendcon Administrator to view what MultiSendcon does in real-time and to configure the accounts and options: Click Configure to open the configuration. There are only four configuration tabs: - Master relay – to configure on which IP and port the MultiSendcon relay server resides. - Relay servers – where you add the SMTP accounts and relay servers to distribute to. - NDR handling – for options regarding non-delivery reports. - License – for the MultiSendcon license. You can run MultiSendcon in evaluation mode for 30 days and enter the license code here to convert into a fully licensed version. On the Master relay screen just select one of your local IP addresses as the one where the MultiSendcon service will be reachable on for Exchange. Please leave the port number 2500 as it is for now. (In case you really need to change it you also need to change the port number in the MultiSendcon Exchange send connector using PowerShell.) You can also limit the access to the MultiSendcon SMTP relay to certain IP addresses and we encourage you to do that to prevent abuse as an open relay by spammers in case your internet router or firewall does not block incoming connections on port 2500 (most do). On the next page, “Relay servers”, you need to add your SMTP relay server accounts that you want MultiSendcon to distribute to: In our example server only two domains are supported – one is our Servolutions.com domain and the other is our sister company, godotandco.com. You need to add your own SMTP relay servers (by the way, “smarthost” is the Exchange word for SMTP relay server – both mean the same thing). See the online help for this screen for more details. Next is the NDR handling setup for how MultiSendcon processes non-delivery reports for those emails that can’t be delivered for some reason: You can select non-delivery messages to go back to the sender or to a postmaster (or both). The only thing you really need to configure here is the IP or DNS name of your Exchange server under SMTP Server . This is the server or IP that MultiSendcon returns NDRs to. You don’t need to configure anything on the License tab for now – that is only for when you finished your evaluation and bought your full license. ### 3. Update the MultiSendcon Send Connector in Exchange to connect to your new MultiSendcon During the MultiSendcon installation a new Exchange send connector will be created for your convenience. The new send connector is already configured to send out emails to port 2500 (instead of the usual 25) but is created disabled (with a cost factor of 100) so you have time to configure MultiSendcon in step 2 before going live with it. You need to change two settings in the send connector to finish this installation: switch the cost factor to 1 (lowest) to make this the active send connector preferred over existing ones and set it to connect to the correct IP address that is monitored by the MultiSendcon service. Open up the Exchange Management Console and go to Organization Configuration > Hub Transport > Send Connectors. You’ll see the new send connector named “MultiSendcon” there. Right-click on it and open up the Properties, then go to the Address Space tab. You’ll see that there is a SMTP “*” address range defined with a cost factor of 100. This means that this connector will never be chosen since all other connectors will have a default cost of 10 or lower. Change it to 1 (lowest) by right-clicking and choosing “edit”. Then change the cost to 1. Next, please go to the Network tab: And edit the default setting of 127.0.0.1 to the actual IP used in the MultiSendcon configuration. In our example (don’t use this IP in your installation) it is the IP 216.18.195.203 as can be seen in the MultiSendcon Admin screen: as well as in the MultiSendcon configuration: For your own configuration please use whatever server IP address you chose in step 2 for the MultiSendcon master SMTP relay and enter it on the Network tab of the new MultiSendcon Exchange send connector: That’s all – now this new Exchange send connector is configured to send email on to the MultiSendcon master SMTP relay and MultiSendcon will take it from there. You can now send a test message and see how it shows up in the MultiSendcon Administrator log and is transferred to the correct SMTP account configured in MultiSendcon. Background: how Exchange chooses between several send connectors, and when its own per-recipient-domain connectors are enough, is explained in the guide Multiple smart hosts in Exchange 2016/2019 . --- ## MultiSendcon System Requirements: Windows and Exchange Source: https://www.servolutions.com/multisendcon/requirements Language: en ### MultiSendcon System Requirements ### Operating System Windows 2025 Server™, Windows 2022 Server™, Windows 2019 Server™, Windows 2016 Server™, Windows 2012 Server™ (incl. R2), Windows 2011 SBS Server™, Windows 2008 Server™ x86 or x64, Windows 2008 SBS Server™, Windows 2003 Server™, Windows 10™, Windows 8™, Windows 7™ ### Compatible Mail Server Software Exchange Server 2019™, Exchange Server 2016™, Exchange Server 2013™, Exchange Server 2010™, Exchange Server 2007™, Exchange Server 2003™, Exchange Server 2000™, and all SBS versions of the above. The MultiSendcon product page also lists Exchange Server SE (Subscription Edition) as supported. What an upgrade to SE means for the MultiSendcon send connector is covered in the guide Exchange Server SE: what changes, what does not . ### Hardware - CPU & Memory: No special requirements - Disk: 10 MB plus the amount needed to temporarily store forwarded emails - Network: One network adapter is sufficient; MultiSendcon also works with two or more cards --- ## MultiSendcon Support — Contact, Install Guide, Help Source: https://www.servolutions.com/multisendcon/support Language: en ### MultiSendcon Support Email and phone support is included with all our products. We respond quickly. Contact: support@servolutions.com ### Installation Guide How to install and configure MultiSendcon → ### Online Help (Administrator Utility) - Administrator Utility overview - Master Relay configuration - Relay Servers configuration - NDR (Non-Delivery Report) handling - License - Advanced settings - SMTP Account settings - Direct DNS / Direct Send settings - Test SMTP Account ### Frequently Asked Questions - “504 5.7.4 Unrecognized authentication type” with Office 365 SMTP relay - Exchange SMTP error codes explained — 504 5.7.4 and the replies Exchange itself returns, with cause and fix - IONOS blocks non-delivery reports and out-of-office messages - How to manually create the Send Connector in Exchange - Service won’t start after upgrading — “ChilkatDotNet47.dll or one of its dependencies could not be found” --- ## Outlook Change FROM Add-in — ChangeSender Source: https://www.servolutions.com/outlook-change-from Language: en ### Outlook Change FROM Add-in: ChangeSender ChangeSender lets Outlook users change the FROM address when sending email through Exchange Server. Send as any of your email addresses or authorized group addresses — the recipient sees the chosen address, not “sent on behalf of.” ### Why You Need This Exchange defaults to the user’s primary email address for all outgoing mail. Replying to an email received on an alternative address still sends from the default. Sharing a single address like info@company.com between team members is not natively supported. ChangeSender fixes both. ### Features - Automatically selects the right FROM address when replying to emails - Sender address dropdown in Outlook for new emails - Multiple users can share a single FROM address - Full control: “Any Name ” - Administrator can restrict available addresses per user - Compatible with Exchange 2000–2019 and Outlook 2000–2024 Download Trial Prices & Shop Full ChangeSender product page → Background: Send As, Send on Behalf, shared mailbox or add-in — the four ways to choose the From address on Exchange on-premises, compared . --- ## POPcon — Exchange POP3/IMAP Connector | Servolutions Source: https://www.servolutions.com/popcon Language: en POP3 / IMAP Connector Latest: v4.10.x ### POPcon ™ Exchange POP3 & IMAP Connector Download email from external POP3 and IMAP mailboxes directly into Microsoft Exchange Server. Automatic distribution to the correct Exchange mailboxes — runs as a Windows service, around the clock. Download Free Trial Prices & Licensing 30-day full-featured trial — no credit card Per-server license, not per-user No reinstallation when you license Capabilities ### What POPcon does 01 POP3 & IMAP Retrieval Connects to any number of external POP3 or IMAP mailboxes on a configurable schedule. Downloads messages and injects them directly into Exchange Server via SMTP or MAPI. 02 Automatic Mail Distribution Analyzes message headers (To:, CC:, X-Envelope-To, Delivered-To, and others) to route each email to the correct Exchange mailbox automatically. No manual sorting required. 03 TLS 1.2 / 1.3 Encryption All connections to remote mail servers use TLS encryption. Supports STARTTLS and implicit TLS on POP3 (port 995) and IMAP (port 993) to keep credentials and mail in transit secure. 04 Windows Service — Runs 24/7 Installs as a native Windows Service. Starts automatically with the server, runs continuously in the background without a logged-in user, and survives reboots without manual intervention. 05 Flexible Scheduling Configure retrieval intervals from 1 minute to 24 hours per mailbox. Run immediate on-demand polls from the management console at any time. Adjust per-account to match your mail volume. 06 Multi-Mailbox Management Manage dozens or hundreds of POP3/IMAP accounts from a single console. Import account lists in bulk, clone configurations, and monitor all connections from one place. 07 Bounce & NDR Handling Routes undeliverable messages (NDRs) to a designated catch-all mailbox rather than discarding them. Keeps a complete record of delivery failures for investigation. 08 Detailed Logging Maintains a rolling log of all retrieval activity: connection attempts, message counts, delivery confirmations, and errors. Essential for diagnosing delivery issues without guessing. Editions ### POPcon vs POPcon PRO Choose the edition that matches your environment. POPcon Standard Edition Most Popular - POP3 & IMAP retrieval into Exchange - TLS 1.2 / 1.3 encryption - Automatic header-based mail distribution - Windows Service — 24/7 operation - Configurable polling schedules - Multi-mailbox management console - NDR / bounce handling - Detailed activity logging - Built-in antivirus scanning - Built-in antispam filtering - Parallel download threads - Mail archiving Download Free Trial View pricing → POPcon PRO Advanced Edition High Volume - Everything in POPcon Standard - TLS 1.2 / 1.3 encryption - Automatic header-based mail distribution - Windows Service — 24/7 operation - Configurable polling schedules - Multi-mailbox management console - NDR / bounce handling - Detailed activity logging - Built-in antivirus scanning - Built-in antispam filtering - Parallel download threads - Mail archiving Learn about PRO → Compatibility ### Runs on every Exchange version ### Exchange Server Exchange 4.5 Exchange 5.0 Exchange 5.5 Exchange 2000 Exchange 2003 Exchange 2007 Exchange 2010 Exchange 2013 Exchange 2016 Exchange 2019 Exchange SE All SBS Versions ### Operating System Windows Server 2012 Windows Server 2016 Windows Server 2019 Windows Server 2022 Windows Server 2025 Windows 7–11 Exchange Configuration ### Set up your Exchange Server for POPcon Step-by-step guides for every Exchange version we support — from new Exchange Server SE deployments to legacy Exchange 5.5 boxes still running in the wild. Pick the matching version below. Exchange 2013 / 2016 Accepted domains, Send Connector to your ISP smart host, anonymous Receive Connector, Email Address Policy, POPcon setup. Read guide → Exchange 2010 incl. SBS 2011 Hub Transport configuration, accepted domains, anonymous SMTP submission for POPcon, smart host send connector. Read guide → Exchange 2007 incl. SBS 2008 Receive Connector for anonymous submission, smart host setup, message size limits, recipient resolution. Read guide → Exchange 2003 SMTP Virtual Server configuration, recipient policy, smart host relay setup, Internet Mail Service replacement. Read guide → Exchange 2000 Recipient policy, SMTP Virtual Server, Internet Mail Connector replacement, mailbox addressing. Read guide → Exchange 5.5 Internet Mail Service configuration, recipient mailbox setup, legacy SMTP submission options. Read guide → ### Common Exchange + POPcon issues - “530 5.7.1 Client was not authenticated” from Exchange - “550 5.7.1 Unable to relay” from Exchange - Exchange does not accept emails larger than 10 MB - “452 4.3.1 Insufficient system resources” - “451 4.7.0 Temporary server error” on Exchange 2013 - “421 4.4.1 Connection timed out” - “Must issue a STARTTLS command first” - Why POPcon needs the “accepted domains” setting - Transfer POPcon settings to a new Exchange server - Microsoft 365 / Outlook online with OAuth2 View the full Knowledge Base → Support & FAQ ### Common questions ### How does POPcon distribute emails to the right Exchange mailboxes? POPcon analyzes message headers — To:, CC:, X-Envelope-To, Delivered-To, and others — to identify the intended recipient, then delivers each message directly to that Exchange mailbox. You can also configure catch-all rules for messages that don't match a specific address. ### Can POPcon connect to Gmail or Microsoft 365 with OAuth? Yes. POPcon v4.8.1+ supports OAuth 2.0 (modern authentication) for both Google and Microsoft accounts. The OAuth setup wizard in POPconAdmin guides you through the authorization flow. No password storage required. Background and the seven steps for Microsoft 365: Basic authentication is gone: Microsoft 365 by IMAP with OAuth2 . ### How do I configure Exchange to accept connections from POPcon? You need to configure an Exchange Receive Connector to accept SMTP connections from the POPcon server's IP address. Our Knowledge Base has step-by-step guides for every Exchange version from 5.5 through 2019. The guide How to download POP3 and IMAP mailboxes into Exchange 2016, 2019 and SE walks through the receive connector and the POPcon setup in four steps. ### Exchange is rejecting POPcon emails with "530 5.7.1 Client was not authenticated" This means the Exchange receive connector only accepts authenticated connections. POPcon hands mail to Exchange the way mail arrives from the internet: over SMTP without authentication. Do not work around the error with SMTP authentication — Exchange would then show every downloaded email as sent by the account used to log in. Instead, open the Default Frontend receive connector (Exchange 2013 and later; the default receive connector on 2007/2010) and tick Anonymous users under Security / Permission Groups, as shown in the Exchange configuration guide and the knowledge base article . ### Can I retrieve from multiple POP3/IMAP accounts? Yes, POPcon handles as many accounts as you need from a single installation. Each account can be configured with its own retrieval interval, protocol (POP3 or IMAP), credentials, and distribution rules. Manage them all from the POPconAdmin console. ### How do I move my POPcon installation to a new server? Use File > Export Config in POPconAdmin to save your configuration. Install POPcon on the new server and use File > Import Config. All account settings transfer. Exchange Receive Connector settings may need to be updated to reflect the new server's IP address. ### Emails are stuck in the queue or not reaching Exchange Check the POPcon log file first — it records each connection attempt and SMTP response. Common causes: port 25 blocked on the Exchange server, Receive Connector not configured for the POPcon IP, or Exchange message size limits. See our Knowledge Base for specific error codes. ### What Exchange versions are supported? Exchange 4.5 through Exchange 2019, plus Exchange Server SE, and all SBS (Small Business Server) versions. Also compatible with Lotus Notes Domino for legacy deployments. Runs on Windows Server 2012–2025 and Windows 7–11. More answers in the full Knowledge Base (60+ articles). Email support directly Release History ### Version history 2026 v4.10.4 June 07, 2026 Stability release. Fixes a service start failure after the 4.10 OAuth migration (empty token-expiry value) and protects the configuration from being overwritten by a failed load. No new features. v4.10.0 May 19, 2026 Microsoft OAuth modernized: new public-client app registration, no client_secret shipped, PKCE-only. One-time re-authentication required for existing Microsoft accounts. v4.9.11 March 09, 2026 Installs additional libraries for new version of antivirus update engine. v4.9.9 March 03, 2026 Automatically cleans up antispam blacklist server list. Diagnostic logging for antivirus update failures. v4.9.8 March 02, 2026 Bugfix: Crashes when loading config with OAuth references. POPconAdmin window position validation. Repaired [SPAM] tag injection. v4.9.5 January 07, 2026 Visual C++ Library detection false error fix. New email handling libraries integrated. 2025 v4.9.4 October 31, 2025 New antivirus update process to support new ClamAV updater (PRO). v4.9.2 July 26, 2025 OAuth with Microsoft servers: fixed port allocation issue. v4.9.1 July 17, 2025 Fixed problem with digital SMIME signatures invalidated by X-Header modification. 2024 v4.8.12 December 07, 2024 AV-update fixed. Better error messages for multiple SMTP error responses. v4.8.10 November 21, 2024 New feature: Sender address for Postmaster notifications now configurable. v4.8.1 September 23, 2024 New: OAuth2 modern authentication for both Google and Microsoft accounts. 2023 v4.7.9 May 19, 2023 VC++ Redistributable package installation. Debug info for .NET and VC++ redist in internals.log. v4.7.7 May 01, 2023 Bugfix: Unicode crashes in subject lines. Archiving SPAM tag options. Increased AV compatibility. 2021 v4.5.1 July 03, 2021 Multiple improvements: archive exception handling, antispam list sorting, resizable configuration forms. v4.0 April 11, 2021 New: Parallel download of multiple POP3/IMAP mailboxes (PRO). Improved download speed. TLS 1.2 support. Earlier v3.94 November 17, 2016 Long file names in MIME headers now detected correctly for RULES. v3.80 August 2013 X-Orig-To header support. ESET antivirus greylisting support with automatic retries. v3.70 September 08, 2008 Windows 2008 support. Exchange 2007 extended support. Archive function. v3.20 September 19, 2005 IMAP and IMAP-SSL mailbox support. New antivirus engine. v3.00 April 22, 2005 Catch-all function. POP3 over SSL. Regular expression support. View full version history → ### Start your 30-day trial today Full-featured. No credit card. When you buy a license, just enter your key — no reinstallation needed. Download POPcon View Pricing Ask a Question --- ## POPcon NOTES — Lotus Notes POP3 Connector Source: https://www.servolutions.com/popcon-notes Language: en ### POPcon NOTES — Lotus Notes POP3 Connector Notice: POPcon NOTES has been retired. Its Lotus Notes / Domino server support is now fully integrated into POPcon and POPcon PRO. Both products work with Domino servers — enter your NOTES server name in the Exchange server name field. ### Recommended Products - POPcon — POP3/IMAP connector for Exchange and Domino servers - POPcon PRO — includes antivirus, antispam, and rule-based distribution --- ## POPcon PRO — Exchange POP3/IMAP Connector with Antivirus Source: https://www.servolutions.com/popcon-pro Language: en POP3 / IMAP Connector PRO ### POPcon PRO ™ Advanced Exchange POP3 & IMAP Connector Everything in POPcon, plus built-in antivirus scanning, antispam filtering, rule-based distribution, and mail archiving. Built for high-volume and security-conscious Exchange environments. Download Free Trial Prices & Licensing 30-day full-featured trial — no credit card Per-server license, one-time fee Exchange 4.5 – 2019, + Exchange SE PRO Features ### Everything in POPcon, plus POPcon PRO adds security and filtering capabilities on top of the core POP3/IMAP retrieval engine — no separate antivirus gateway required. ### Built-in Antivirus Scanning Each incoming message is scanned automatically. Infected emails are wrapped in a warning message and routed to the postmaster. Virus signatures update daily without manual intervention. ### Antispam Filtering Checks sender IPs against real-time blacklist servers (RBLs). Configurable spam tag injection and auto-delete rules. Blacklist server list is automatically cleaned and updated. ### Rule-Based Distribution Define rules by sender address, recipient name, subject line, or attachment filename. Actions: forward, copy, delete, or reroute. Unlimited rules, evaluated in priority order. ### Mail Archiving Optionally archive every received message to configurable daily or monthly folders. Keeps an audit trail independent of Exchange mailbox storage. ### Parallel Download Threads Download from multiple POP3/IMAP accounts simultaneously using parallel threads. Significantly faster retrieval in high-volume or many-account deployments. ### Excel-Importable Message Logs Detailed per-message logs exportable as CSV for import into Excel. Track delivery counts, error rates, spam flags, and virus detections over time. Included Features ### Core POPcon functionality POPcon PRO includes the complete POPcon feature set. All standard retrieval, distribution, and compatibility features are part of the base product. View POPcon feature details - POP3 & IMAP retrieval into Exchange Server - Automatic mail distribution to correct Exchange mailboxes - TLS 1.2 / 1.3 encryption for all connections - Runs as Windows Service — 24/7 unattended operation - Configurable per-mailbox retrieval intervals (1 min – 24 hr) - Multi-mailbox management from a single console - Bounce & NDR handling to catch-all mailbox - OAuth 2.0 modern authentication (Gmail, Microsoft 365) - Exchange 4.5 – 2019, + Exchange SE compatibility Exchange Configuration ### Set up your Exchange Server for POPcon PRO POPcon PRO uses the same Exchange-side configuration as POPcon. Follow the guide for your Exchange version, then enter your PRO license key on first run to activate the antivirus, antispam, rules and archiving features. Exchange 2013 / 2016 Accepted domains, Send Connector to your ISP smart host, anonymous Receive Connector, Email Address Policy, POPcon PRO setup. Read guide → Exchange 2010 incl. SBS 2011 Hub Transport configuration, accepted domains, anonymous SMTP submission for POPcon PRO, smart host send connector. Read guide → Exchange 2007 incl. SBS 2008 Receive Connector for anonymous submission, smart host setup, message size limits, recipient resolution. Read guide → Exchange 2003 SMTP Virtual Server configuration, recipient policy, smart host relay setup, Internet Mail Service replacement. Read guide → Exchange 2000 Recipient policy, SMTP Virtual Server, Internet Mail Connector replacement, mailbox addressing. Read guide → Exchange 5.5 Internet Mail Service configuration, recipient mailbox setup, legacy SMTP submission options. Read guide → ### Common Exchange + POPcon PRO issues - “530 5.7.1 Client was not authenticated” from Exchange - “550 5.7.1 Unable to relay” from Exchange - Exchange does not accept emails larger than 10 MB - “452 4.3.1 Insufficient system resources” - “451 4.7.0 Temporary server error” on Exchange 2013 - “421 4.4.1 Connection timed out” - “Must issue a STARTTLS command first” - Why POPcon needs the “accepted domains” setting - Transfer POPcon settings to a new Exchange server - Microsoft 365 / Outlook online with OAuth2 View the full Knowledge Base → Support & FAQ ### Common questions ### What's the difference between POPcon and POPcon PRO? POPcon PRO includes everything in POPcon plus built-in antivirus scanning, antispam filtering (RBL checks), rule-based message distribution, mail archiving, and parallel download threads. If you need virus protection or advanced filtering without a separate gateway, PRO is the right choice. ### Can I upgrade from POPcon to POPcon PRO? Yes. Contact sales@servolutions.com with your existing POPcon license details. We'll provide an upgrade pricing quote and a single PRO installer — no reinstallation of Exchange configuration required. ### How does the antivirus engine work? POPcon PRO includes an embedded antivirus scanner with automatic daily signature updates. Detected virus emails are encapsulated in a warning message and optionally diverted to the postmaster address rather than delivered to the recipient. ### The antispam is marking legitimate emails as spam. What should I do? The antispam uses RBL (real-time blackhole list) servers. False positives can happen when a sending server's IP is on a blacklist. Check the POPconAdmin log to identify which blacklist triggered, and consider adding that server to your whitelist or disabling that specific RBL. ### How do I set up Gmail or Microsoft 365 with OAuth? POPcon PRO v4.8.1+ supports OAuth 2.0 for both Google and Microsoft accounts. The setup wizard in POPconAdmin guides you through the authorization flow. See our step-by-step Knowledge Base guides for Gmail and Microsoft 365 . ### Where are the archived emails stored? Archived emails are saved to a configurable folder path on the server running POPcon PRO, organized in daily or monthly subfolders. The archive is independent of Exchange — it stores raw .eml files for compliance or backup purposes. ### How do I transfer my configuration to a new server? Export your configuration from POPconAdmin on the old server (File > Export Config). On the new server, install POPcon PRO and use File > Import Config. All mailbox accounts, rules, and settings are transferred. See the Knowledge Base migration guide for full details. ### What Windows versions are supported? Windows Server 2012, 2016, 2019, 2022, 2025 — and Windows 7 through 11 for non-server deployments. Requires .NET 4.7.2 or later. More answers in the full Knowledge Base (60+ articles). Email support directly Release History ### Version history POPcon PRO shares its version history with POPcon. Showing recent releases. View full history → 2026 v4.10.4 June 07, 2026 Stability release. Fixes a service start failure after the 4.10 OAuth migration (empty token-expiry value) and protects the configuration from being overwritten by a failed load. No new features. v4.10.0 May 19, 2026 Microsoft OAuth modernized: new public-client app registration under Servolutions IP Corporation, no client_secret shipped, PKCE-only. One-time re-authentication required for existing Microsoft accounts. v4.9.11 March 09, 2026 Installs additional libraries for new version of antivirus update engine. v4.9.9 March 03, 2026 Automatically cleans up antispam blacklist server list, removing defunct servers and updating names. Diagnostic error logging for antivirus update failures. v4.9.8 March 02, 2026 Bugfix: Crashes when loading a config file from a different server with OAuth references. POPconAdmin window position validation. Repaired [SPAM] tag injection function. v4.9.7 February 27, 2026 Additional diagnostics for antispam checking. v4.9.6 February 26, 2026 Visual C++ Library detection fix for v14+ redistributables. v4.9.5 January 07, 2026 Visual C++ Library detection false error fix. New version of email handling libraries integrated. 2025 v4.9.4 October 31, 2025 New antivirus update process to support new ClamAV updater. v4.9.2 July 26, 2025 OAuth with Microsoft servers: fixed port allocation issue by selecting ports 8080–8084. v4.9.1 July 17, 2025 Fixed problem with digital SMIME signatures invalidated by X-Header modification. 2024 v4.8.12 December 07, 2024 AV-update fixed. Better error messages for multiple SMTP error responses. v4.8.11 November 21, 2024 Bugfix: Exchange email address resolution on Windows 2022 servers. v4.8.10 November 21, 2024 New feature: Sender address for Postmaster notifications now configurable. v4.8.9–4.8.7 October–November 2024 Several archive improvements. Upgraded AV core engine. Encrypted AV update path. v4.8.1 September 23, 2024 New: OAuth2 modern authentication for both Google and Microsoft accounts. 2023 v4.7.9 May 19, 2023 VC++ Redistributable package installation. Debug info for .NET and VC++ redist in internals.log. v4.7.7 May 01, 2023 Bugfix: Unicode character crashes in subject lines. Archiving with/without SPAM tags. Increased AV system compatibility. 2022 v4.6.9 June 30, 2022 Timeout extended for POP3 server connections. Antivirus disabled state now reported correctly. v4.6.2 January 26, 2022 New: X-FORWARDED-FOR header support for catch-all mailbox distribution. 2021 v4.5.1 July 03, 2021 Multiple improvements: archive exception handling, antispam list sorting, resizable configuration forms. v4.0 April 11, 2021 New: Parallel download of multiple POP3/IMAP mailboxes. Improved download speed. TLS 1.2 support. --- ## POPcon PRO Antispam Blacklist Servers (DNSBL) Source: https://www.servolutions.com/popcon-pro/blacklists Language: en ### POPcon PRO Antispam Blacklist Servers We are currently using these spam list servers in our own configuration with very good success (high spam detection rate with low false positives): - blackholes.mail-abuse.org (list name: “MAPS RBL”) - bl.spamcop.net (list name: “Spamcop”) - sbl.spamhaus.org (list name: “Spamhaus SBL”) - cbl.abuseat.org (list name: “Composite blocking list”) - ix.dnsbl.manitu.net - dnsbl-1.uceprotect.net - dnsbl-2.uceprotect.net ### Configuration Tips If you add or change the blocking/spam list server settings it is always a good idea to switch from having POPcon PRO deleting the spam messages to tagging them in the subject line instead. This way you can monitor which messages are being flagged as spam for a period of time without actually losing any important messages. ### How We Configured Our Own System We added all of the above spam list servers and let POPcon PRO tag the emails with “[SPAM]” in the subject. Then we configured a simple Outlook rule that moves all emails tagged [SPAM] to a special mail folder. Once a week we go through this folder to sort out any wrongly tagged emails. This only takes a couple of minutes every week. Normally there are none, but we do receive the occasional support inquiry from a legitimate business that has the misfortune to be routed through a heavily spam-trafficked server. --- ## POPcon PRO Download — v4.10.4 for Exchange 2007–2019, Trial Source: https://www.servolutions.com/popcon-pro/download Language: en ### Download POPcon PRO Current version: POPcon PRO v4.10.4 Download POPcon PRO v4.10.4 For 64-bit Exchange 2019, 2016, 2013, 2010 or 2007. SHA-256: 75a16a7b2277c2f84296a6c48e4213e2b2d38fa27b1d37103adf8591eb388a68 ### What's new in v4.10.4 POPcon 4.10.4 is a stability release for the 4.10 series. There are no new features and no configuration changes. - Service no longer fails to start after the update. On some accounts the 4.10 OAuth migration could leave the stored token-expiry value empty, which stopped the service in 4.10.3. POPcon now tolerates an empty or missing value and simply refreshes the Microsoft 365 token on the next poll. - A failed configuration load can no longer wipe your working configuration. The service now writes its configuration atomically (keeping a .bak copy), and a configuration file that does not parse is treated as a failed load — the existing file is never overwritten. Your accounts are preserved. Recommended for anyone running a 4.10.x version, especially installations that went through the Microsoft 365 / OAuth re-consent during the 4.10 upgrade. This is an in-place upgrade — your accounts and settings are kept and no re-authorisation is needed. ### Trial & Licensing - Test the full product for 30 days without any restrictions - This version automatically converts to the full, non-time-limited product once you enter a license key - Upgrade from v3.x to v4.x is free only for licenses bought within the last 12 months ### Upgrade Instructions - Uninstall the old version. All your configuration settings will be kept in the registry. - Run the new installer. Configuration settings are imported automatically. ### Additional Utilities - POPconTrigger — triggers mail retrieval from the command line - POPconView — monitoring tool without configuration access View full version history · Order license --- ## POPcon PRO Features — Antivirus, Antispam, Archive, Rules Source: https://www.servolutions.com/popcon-pro/features Language: en ### POPcon PRO Features ### PRO-Exclusive Features - Antivirus Engine: Built-in internal anti-virus engine scans every incoming email before relaying it to your Exchange server. Updates occur weekly or daily via automatic signature downloads. - Archive Function: Archives all downloaded emails into separate folders on the server. Can be configured to create individual daily or monthly archive folders. - Antispam Protection: Checks IP addresses in the headers of incoming emails against internet spam blacklist servers. - Rule-Based Distribution: Forward, send a copy, or delete an email if it meets user-configured conditions. Rules can target recipient names, sender addresses, subject lines, or attachment filenames. - Message Logging: Excel-importable detailed message logs. - Parallel Downloads: Simultaneous download of multiple POP3 or IMAP mailboxes for improved performance. ### Standard Features (also in POPcon) - Poll private POP3 and IMAP mailboxes; forward to Exchange or distribute catch-all mail to multiple mailboxes - Minimum download interval: 1 minute (or continuous with 0-minute option) - Flexible scheduling based on day of week - Automatic dial-up networking support - POPcon Administrator utility for network-wide monitoring - Installed as a Windows service with automatic startup - TLS 1.2 and TLS 1.3 support - OAuth2 modern authentication for Google and Microsoft accounts ### Email Flow Incoming: Senders → POP3/IMAP mailboxes → POPcon PRO downloads → antivirus check → antispam check → rules engine → Exchange Server via SMTP. Outgoing: Handled directly by your Exchange Server. Download Trial --- ## POPcon PRO Version History Source: https://www.servolutions.com/popcon-pro/history Language: en ### POPcon PRO Version History POPcon PRO shares the same version history as POPcon. View the full version history → --- ## POPcon PRO System Requirements — Windows & Exchange Source: https://www.servolutions.com/popcon-pro/requirements Language: en ### POPcon PRO System Requirements ### Operating System Windows 2025 Server™, Windows 2022 Server™, Windows 2019 Server™, Windows 2016 Server™, Windows 2012 Server™ (incl. R2), Windows 2011 SBS Server™, Windows 11™ x86 or x64, Windows 10™ x86 or x64, Windows 8™, Windows 7™ ### Compatible Mail Server Software Exchange Server SE™, Exchange Server 2019™, Exchange Server 2016™, Exchange Server 2013™, Exchange Server 2010™, Exchange Server 2007™, Exchange Server 2003™, Exchange Server 2000™, and all SBS versions of the above. Also compatible with: Lotus Domino/Notes™, Tobit David™, Apple Mac OS Lion Mail Server. ### Hardware - CPU & Memory: No special requirements - Disk: 10 MB plus the amount needed to temporarily store downloaded emails before they are forwarded to Exchange - Network: One network adapter is sufficient; POPcon PRO also works with two or more cards ### Internet Connection Any internet connection via dial-up or routers, as long as POPcon PRO can connect to POP3 and IMAP ports on your ISP mailbox servers. --- ## POPcon PRO Support — Exchange Guides, Antispam FAQ Source: https://www.servolutions.com/popcon-pro/support Language: en ### POPcon PRO Support Email and phone support is included with all our products. We respond quickly. Contact: support@servolutions.com ### Exchange Server Configuration Guides - Configuration of Exchange 2013 or 2016 Server - Configuration of Exchange 2010 Server (incl. SBS 2011) - Configuration of Exchange 2007 Server (incl. SBS 2008) - Configuration of Exchange 2003 Server - Configuration of Exchange 2000 Server - Configuration of Exchange Server 5.5 ### Frequently Asked Questions The Knowledge Base covers 60+ FAQ articles including POPcon PRO antispam and antivirus topics. Frequently referenced topics: ### Configuration & Authentication - Gmail with OAuth2 (modern authentication) - Microsoft 365 / Outlook online with OAuth2 - Transfer POPcon PRO settings to a new server ### Antispam & Antivirus - How the antispam feature works and why it is not 100% accurate - Can I use wildcards like `*@spammer.com` in the anti-spam blacklist? - Antispam is taking 30 seconds per message - Diagnose malfunctioning antispam blacklist servers - All emails are suddenly tagged as SPAM - “[blacklist] could not be tested and will not be used” - Windows DEP is crashing the antivirus engine - Virus scanner deletes .msg files — POPcon hangs ### Email Delivery Issues - “530 5.7.1 Client was not authenticated” from Exchange - “550 5.7.1 Unable to relay” from Exchange - Exchange does not accept emails larger than 10 MB - IONOS blocks non-delivery reports and out-of-office messages View full Knowledge Base → --- ## POPcon Download — Exchange POP3/IMAP Connector, Free Trial Source: https://www.servolutions.com/popcon/download Language: en ### Download POPcon Current version: POPcon v4.10.4 Download POPcon v4.10.4 For 64-bit Exchange 2019, 2016, 2013, 2010 or 2007. SHA-256: 75a16a7b2277c2f84296a6c48e4213e2b2d38fa27b1d37103adf8591eb388a68 ### What's new in v4.10.4 POPcon 4.10.4 is a stability release for the 4.10 series. There are no new features and no configuration changes. - Service no longer fails to start after the update. On some accounts the 4.10 OAuth migration could leave the stored token-expiry value empty, which stopped the service in 4.10.3. POPcon now tolerates an empty or missing value and simply refreshes the Microsoft 365 token on the next poll. - A failed configuration load can no longer wipe your working configuration. The service now writes its configuration atomically (keeping a .bak copy), and a configuration file that does not parse is treated as a failed load — the existing file is never overwritten. Your accounts are preserved. Recommended for anyone running a 4.10.x version, especially installations that went through the Microsoft 365 / OAuth re-consent during the 4.10 upgrade. This is an in-place upgrade — your accounts and settings are kept and no re-authorisation is needed. ### Trial & Licensing - Test the full product for 30 days without any restrictions - This version automatically converts to the full, non-time-limited product once you enter a license key - Upgrade from v3.x to v4.x is free only for licenses bought within the last 12 months ### Upgrade Instructions - Uninstall the old version. All your configuration settings will be kept in the registry. - Run the new installer. All your configuration settings will be imported from any old installation automatically. ### Additional Utilities (POPcon PRO) - POPconTrigger — triggers mail retrieval from the command line - POPconView — monitoring tool without configuration access View full version history · Order license --- ## POPcon Features — POP3/IMAP to Exchange, Catch-all Mail Source: https://www.servolutions.com/popcon/features Language: en ### POPcon Features - Poll private POP3 and IMAP mailboxes and forward mail to a single MS Exchange Server™ mailbox, or distribute mail collected in a single catch-all POP3 or IMAP mailbox to multiple MS Exchange Server™ mailboxes - Analyzes mail header fields (TO:, CC:, received..for, X-RESENT-TO, etc.) and filters recipients matching pre-configured allowed domains - Minimum download schedule interval: 1 minute. Also supports 0 minutes (continuous downloads) - Handles downloads exceeding scheduled intervals by continuing at the next full minute - Installable on the same machine as MS Exchange Server™ using one internet connection - Flexible scheduling for mail retrieval based on day of week - Automatically uses configurable dial-up networking; supports routers and dedicated connections - Includes “POPcon Administrator” utility for network-wide monitoring and remote configuration - POPcon is installed as a service and started at system startup time without the need for a user to log in - TLS 1.2 and TLS 1.3 support - OAuth2 modern authentication for Google and Microsoft accounts ### Email Flow Incoming: Senders transmit via SMTP to POP3/IMAP mailboxes → POPcon periodically downloads via POP3/IMAP → POPcon delivers to Exchange Server via SMTP. Outgoing: POPcon is only used for incoming emails. Outgoing mail is handled directly by your Exchange Server. Download Trial --- ## POPcon Advanced Configuration Options Source: https://www.servolutions.com/popcon/features/advanced Language: en ### POPcon Advanced Configuration Options ### Eventlog Entries POPcon can write status and error information to the Windows eventlog. Use this option to enable or disable eventlog entries as needed. When enabled, POPcon logs each mail retrieval cycle, errors, and key processing events to the Application log. ### Recipient Address Manipulation POPcon allows you to remove a configurable string from the start or end of recipient mail addresses before delivery. This is useful when your external mail provider adds prefixes or suffixes to addresses that do not match your internal Exchange or SMTP server addresses. - Remove string from start of recipient address — strips a fixed prefix from each recipient address. - Remove string from end of recipient address — strips a fixed suffix from each recipient address. - Regular expression support — both fields accept PERL-type regular expressions for complex pattern matching. This enables flexible transformations such as stripping variable-length substrings or rewriting address patterns. ### Remove Read Receipt Requests When enabled, POPcon strips read receipt request headers ( Disposition-Notification-To ) from incoming messages before delivery. This prevents internal users from inadvertently sending read confirmations to external senders. ### Processed Mail Header Fields POPcon examines specific mail header fields to determine the intended recipient of each message. The following header fields can be individually enabled or disabled: - Received…for — parses the Received header’s “for” clause to extract the envelope recipient address. - Delivered-To — uses the Delivered-To header field, commonly set by providers such as Gmail and other large mail hosts. Enable or disable each option via its corresponding checkbox. In most configurations, both options should remain enabled to ensure accurate recipient detection. ### Replacement of Domain Names The domain replacement feature maps external domain names to internal domain names. This is required when your external-facing mail domain differs from the domain used on your internal Exchange or SMTP server. For example, if your provider delivers mail addressed to user@example.com but your internal server expects user@internal.local , you can add a mapping from example.com to internal.local . POPcon rewrites the recipient domain before forwarding the message via SMTP. - Multiple domain mappings can be configured simultaneously. - Mappings apply to all recipient addresses extracted from mail headers. --- ## POPcon Internet Connection / Dial-up Source: https://www.servolutions.com/popcon/features/connection Language: en ### POPcon Internet Connection / Dial-up ### Direct Connection Select Direct Connection when your server has permanent internet access through a router, gateway, or another computer sharing its connection. In this mode, POPcon assumes the network is always available and initiates mail retrieval according to the configured schedule without establishing or tearing down a connection. ### Dial-Up Connection Select Dial-Up Connection when POPcon must establish an internet connection before retrieving mail. Configure the following fields for the dial-up entry: - Username — the account name required by your ISP or dial-up provider. - Password — the corresponding password for authentication. POPcon will automatically dial the configured connection at the start of each mail retrieval cycle and disconnect when the cycle completes. ### Do Not Disconnect When the “Do not disconnect” option is enabled, POPcon will not hang up the dial-up connection after completing a mail retrieval cycle. This is useful when other applications share the same dial-up connection and you do not want POPcon to interrupt them. ### Trigger Mail When Dial-Up Connection Active Enable “Trigger mail when dial-up connection active” to have POPcon automatically start a mail retrieval cycle whenever it detects that a dial-up connection has been established — regardless of the current schedule. This ensures mail is downloaded promptly each time the connection becomes available. ### Proxy Server Configuration If your network routes outbound traffic through a proxy server, POPcon can be configured to use it. Specify the proxy server address and port so that POP3 and IMAP connections are routed correctly. Consult your network administrator for the appropriate proxy settings. --- ## POPcon General Options Source: https://www.servolutions.com/popcon/features/general Language: en ### POPcon General Options ### Postmaster Email Address Configure the postmaster email address to specify which mailbox receives messages that POPcon cannot deliver to a valid recipient. When POPcon processes a message and no matching recipient exists on the internal mail server, the message is forwarded to the postmaster address instead of being discarded. Important: The postmaster address does not receive all emails addressed to unknown users. Emails addressed to unknown recipients within a specific POP3/IMAP account are handled by that account’s own “Re-route mail” setting. The postmaster address is only used as a final fallback when no other routing rule applies. ### Log File Configuration POPcon maintains a log of all mail retrieval activity, errors, and processing events. Two logging modes are available: - Single log file with size limit — POPcon writes all log entries to a single file. When the file reaches the configured maximum size, it is truncated or rotated to prevent unbounded disk usage. This mode is suitable for environments where a simple, compact log is sufficient. - Daily log files — POPcon creates a new log file for each day, using the date as part of the filename. This mode simplifies log review and archival, as each file covers exactly one day of activity. Old daily log files can be deleted or archived independently. --- ## POP3/IMAP Configuration Settings Source: https://www.servolutions.com/popcon/features/pop3 Language: en ### POP3/IMAP Configuration Settings ### Adding POP3/IMAP Accounts Each external mailbox that POPcon should retrieve mail from is configured as an individual POP3 or IMAP account. Add as many accounts as needed — POPcon processes them sequentially during each mail retrieval cycle. ### Accepted Recipient Domains For catch-all mailboxes, configure one or more accepted recipient domains . POPcon uses these domains to filter incoming messages: only emails addressed to recipients within the listed domains are forwarded to the internal mail server. This prevents unrelated messages from being delivered when the external mailbox collects mail for multiple domains. ### Max Emails per Download Pass Set the maximum number of emails POPcon retrieves from an account in a single download pass. This limit helps control bandwidth and processing time, particularly for accounts that accumulate a large volume of messages between retrieval cycles. ### Server Types and Port Numbers POPcon supports the following server types for connecting to external mail providers (which one to pick per provider, and how the encryption setting and the port belong together, is explained in the guide POP3 or IMAP for retrieving provider mailboxes into Exchange? ): - POP3 — standard POP3 connection (default port 110). - POP3-SSL — POP3 over SSL/TLS (default port 995). - IMAP — standard IMAP connection (default port 143). - IMAP-SSL — IMAP over SSL/TLS (default port 993). The SSL ports 995 and 993 expect the connection to be encrypted before the first command (implicit TLS); on 110 and 143 the connection starts in plain text and can be upgraded with STARTTLS. Which encryption value belongs to which port, and the error a mismatch produces, is explained in the guide POP3/IMAP over TLS for mail retrieval: ports 995 and 993, STARTTLS vs implicit TLS . ### Access Settings Each account requires the following access parameters: - Server name — the hostname or IP address of the external mail server. - Username — the login name for authenticating with the mail server. - Password — the corresponding password for the account. - Port — the TCP port number (defaults depend on the selected server type). - Timeout — the number of seconds POPcon waits for a server response before treating the connection as failed. ### Mailbox Types POPcon distinguishes between two mailbox types: - Catch-all mailbox — collects mail for multiple recipients. POPcon examines message headers to determine the intended recipient and delivers each message to the corresponding internal mailbox. A re-route address can be configured to receive messages whose recipients cannot be resolved. - Single-user mailbox — all mail retrieved from this account is delivered to one specific internal recipient, regardless of the addresses in the message headers. Which type suits your provider and your users, including the BCC and mailing-list cases, is compared in the guide Catch-all (multidrop) mailbox vs one POP3 mailbox per user . ### Delete / Keep Email Options After downloading messages, POPcon can handle mail on the remote server in one of the following ways: - Delete emails from server — messages are removed immediately after successful download. - Leave emails on server indefinitely — messages remain on the remote server and are not deleted by POPcon. - Leave emails on server for N days — messages are kept on the remote server for the specified number of days, then deleted. This provides a window for other clients to retrieve the same messages. --- ## POPcon Mail Cycle Scheduling Source: https://www.servolutions.com/popcon/features/schedule Language: en ### POPcon Mail Cycle Scheduling ### Simple Scheduling Simple scheduling configures POPcon to wait a fixed number of minutes between mail retrieval cycles. After each cycle completes, POPcon pauses for the specified interval before starting the next cycle. - The minimum interval is 1 minute . Setting the interval to 0 enables continuous retrieval — POPcon starts the next cycle immediately after the previous one finishes, with no pause in between. Simple scheduling is appropriate for most environments where mail should be retrieved at a consistent frequency throughout the day. ### Complex Scheduling Complex scheduling provides fine-grained control by allowing you to specify exact retrieval times on a per-weekday basis. For each day of the week, you can define one or more specific times at which POPcon should initiate a mail retrieval cycle. Use the following controls to manage the schedule: - Add — adds a single retrieval time for the selected weekday. - Add Multiple — adds multiple retrieval times at once (e.g., every 30 minutes within a specified range). - Remove — removes the selected retrieval time from the schedule. - Remove All — clears all retrieval times for the selected weekday. Complex scheduling is useful for environments where mail retrieval should occur frequently during business hours but less often (or not at all) during nights and weekends. --- ## POPcon SMTP/Exchange Server Settings Source: https://www.servolutions.com/popcon/features/smtp Language: en ### POPcon SMTP/Exchange Server Settings ### Exchange Server Name Enter the hostname or IP address of the internal Exchange or SMTP server that POPcon delivers retrieved mail to. This is the server that accepts incoming messages via SMTP and routes them to individual user mailboxes. ### SMTP Port Specify the TCP port on which the target SMTP server listens for incoming connections. The default value is 25 , which is the standard SMTP port. Change this only if your server uses a non-standard port configuration. ### SMTP Timeout Configure the number of seconds POPcon waits for a response from the SMTP server before treating the connection as failed. Increase this value if your server is slow to respond under heavy load; decrease it to detect unresponsive servers more quickly. ### Advanced Error Handling POPcon provides configurable responses to specific SMTP error conditions encountered during message delivery. The following error types can be individually configured: - User unknown — the SMTP server rejected the recipient address because no matching mailbox exists. Configure whether POPcon should re-route the message to the postmaster, discard it, or leave it on the remote server for retry. - IP blocked — the SMTP server refused the connection because the sending IP address is blocked or not authorized. This typically indicates a relay restriction or firewall rule. Configure the action POPcon should take when this error occurs. - Action not taken — a general SMTP failure indicating the server could not complete the requested action (e.g., mailbox full, temporary server error). Configure whether POPcon should retry delivery, skip the message, or escalate to the postmaster. --- ## POPcon Account Details — POP3/IMAP Server, OAuth2, TLS Source: https://www.servolutions.com/popcon/help/account-details Language: en ### Account Details ### Server - Server Type: Select POP3 or IMAP depending on your mail provider’s protocol support. - Server Name: The hostname or IP address of the mail server (e.g., mail.example.com ). - Port Number: - POP3: 110 (standard) or 995 (SSL/TLS) - IMAP: 143 (standard) or 993 (SSL/TLS) - Authentication: - Standard — Username and password authentication - OAuth2 Microsoft — Modern authentication for Microsoft 365 and Outlook.com accounts - OAuth2 Google — Modern authentication for Google Workspace and Gmail accounts - Username: The login name for the mail account. - Password: The password for standard authentication. Not used when OAuth2 is selected. - OAuth Status: Displays the current OAuth2 authorization state when OAuth2 authentication is selected. - Encryption: - TLS — Transport Layer Security (implicit, connects on the SSL port) - SSL — Secure Sockets Layer (legacy, connects on the SSL port) - SPA — Secure Password Authentication - STLS — StartTLS (upgrades a plain connection to encrypted) - Timeout: Maximum time in seconds to wait for a server response. Default is 180 seconds. - Max Emails Per Pass: Maximum number of emails downloaded in a single polling cycle. Default is 200 . - Test Access: Click this button to verify the server connection, authentication, and mailbox access. ### Type of Account / Distribution - Single User: All emails from this account are delivered to a single Exchange mailbox. - Catch-All: Emails are distributed to multiple Exchange mailboxes based on recipient address analysis. - Reroute Unknown: When using catch-all distribution, emails with unrecognized recipient addresses are rerouted to a specified default mailbox instead of being rejected. ### Delete / Keep Email Options - Delete emails after download: Removes messages from the remote server once they have been successfully delivered to Exchange. - Keep emails on server: Leaves messages on the remote server after downloading. POPcon tracks which messages have already been processed to avoid duplicates. ### Schedule - Download every N minutes: Sets the polling interval for this account. Minimum interval is 1 minute; a value of 0 enables continuous downloading. - Deactivated: Disables automatic downloading for this account. The account can still be triggered manually. - Limit to work hours: Restricts automatic downloads to configured work hours only, reducing off-hours server connections. --- ## POPcon Help: Managing POP3/IMAP Accounts Source: https://www.servolutions.com/popcon/help/accounts Language: en ### POP3/IMAP Accounts The Accounts page displays all configured POP3 and IMAP accounts and provides controls for managing them. ### Account List Shows all configured accounts with their server name, username, account type, schedule status, and last download time. ### Controls - Add: Opens the Account Details dialog to create a new POP3 or IMAP account configuration. - Edit: Opens the Account Details dialog for the selected account to modify its settings. - Copy + Edit: Creates a duplicate of the selected account and opens it in the Account Details dialog for modification. Useful for setting up multiple accounts with similar configurations. - Remove: Deletes the selected account configuration. This does not affect emails already delivered to Exchange or emails remaining on the remote server. - Show Messages: Displays the messages currently available on the remote server for the selected account without downloading them. - Download Now: Immediately triggers a download for the selected account, regardless of its schedule settings. - Enable / Disable: Toggles the active state of the selected account. Disabled accounts are skipped during scheduled downloads. - Schedule Downloads: Opens schedule configuration to set download intervals and timing constraints for the selected account. --- ## POPcon Help - POPcon Administrator Source: https://www.servolutions.com/popcon/help/admin Language: en ### POPcon Administrator The POPcon Administrator is a utility application for monitoring and managing the POPcon service. It can be run on any machine on the network that has access to the POPcon service. ### Log Window Displays a real-time log of POPcon operations including account polling, email downloads, delivery attempts, errors, and antispam/antivirus activity. The log window scrolls automatically as new entries appear. ### Show Log Update Check this option to enable real-time scrolling of the log window. Uncheck it to freeze the display at the current position, allowing you to review earlier log entries without interruption. ### Controls - Configure: Opens the POPcon configuration dialog to modify accounts, Exchange Server settings, antispam, antivirus, and all other options. - Download Now: Immediately triggers a download cycle for all enabled accounts, regardless of their individual schedules. - Exit: Closes the POPcon Administrator window. Note: Closing the POPcon Administrator does not stop the POPcon service. The service continues to run in the background and process scheduled downloads. To stop the service, use the Windows Services management console. --- ## POPcon Help: Advanced Options Source: https://www.servolutions.com/popcon/help/advanced Language: en ### Advanced Options ### Logging and Thread Management - Event Log: Enable or disable writing operational events to the Windows Event Log for monitoring by external tools. - Concurrent Threads: Set the number of simultaneous download threads to process multiple accounts in parallel. PRO version only. ### Header Fields for Recipient Addresses Select which email header fields POPcon analyzes to determine the recipient address when distributing catch-all emails. Check or uncheck each field as needed: - received-for - Delivered-To - RESENT-TO - X-RESENT-TO - RCPT-TO - To - CC - Envelope-To - X-Envelope-To - X-Original-To - X-Apparently-To The order of fields in the list determines the priority in which they are evaluated. Fields higher in the list take precedence. ### Email Modifications - Remove read receipts: Strips read-receipt request headers (e.g., Disposition-Notification-To ) from incoming emails before delivery. - Remove sensitivity tags: Strips sensitivity headers (e.g., Sensitivity: Private ) from incoming emails before delivery. - Remove string from start of addresses: Specify a prefix string to strip from the beginning of recipient email addresses. Useful for cleaning up addresses modified by the mail provider. ### Recipient Address Handling - Silently drop addresses: Define recipient addresses that should be silently discarded without generating a non-delivery report or notification. - Auto-replace domains: Automatically replace the domain portion of recipient addresses. Useful when the external domain differs from the internal Exchange domain. ### Network Configuration - Local network card for external connections: Select which network interface POPcon uses for outbound connections to remote POP3/IMAP servers. - Local network card for internal connections: Select which network interface POPcon uses for connections to the local Exchange Server. --- ## POPcon Help: Antispam Options (PRO) Source: https://www.servolutions.com/popcon/help/antispam Language: en ### Antispam Options ### Enable Antispam Activates POPcon’s built-in antispam filtering. When enabled, incoming emails are checked against DNS blacklists and user-defined rules before delivery to Exchange. ### DNS Blacklist Servers Configure one or more DNS-based blacklist (DNSBL) servers to check the sending mail server’s IP address against known spam sources. - Add: Add a new DNSBL server address to the list. - Edit: Modify an existing DNSBL server entry. - Remove: Delete a DNSBL server from the list. ### User-defined Whitelist Define rules to always allow emails matching specific criteria, bypassing spam checks. Whitelist entries can match on: - Sender address: The From: header address - Recipient address: The To: or CC: header address - Subject: Text contained in the Subject: header - Attachment name: Filename of an attached file - Header field: Any custom header field and value - Mail text: Text contained in the email body ### User-defined Blacklist Define rules to always flag emails matching specific criteria as spam. Blacklist entries can match on the same criteria as the whitelist: - Sender address: The From: header address - Recipient address: The To: or CC: header address - Subject: Text contained in the Subject: header - Attachment name: Filename of an attached file - Header field: Any custom header field and value - Mail text: Text contained in the email body ### Action for Spam Configure what happens when an email is identified as spam: - Divert to email address: Redirect the spam email to a specified mailbox for review instead of delivering it to the intended recipient. - Tag subject with [SPAM]: Prepend [SPAM] to the email’s subject line and deliver it normally. Recipients can then use mail client rules to filter tagged messages. --- ## POPcon Help - Integrated Anti-virus Options Source: https://www.servolutions.com/popcon/help/antivirus Language: en ### Integrated Anti-virus Options ### Enable Antivirus Activates POPcon’s integrated antivirus scanning. When enabled, all incoming emails and attachments are scanned for malware before delivery to Exchange. ### What to Do with Infected Emails Configure the action taken when an email is found to contain a virus or malware: - Move to badmail folder: The infected email is moved to the configured badmail directory for quarantine and later review by an administrator. - Divert to email address with warning: The infected email is redirected to a specified mailbox with a warning notification attached, allowing an administrator to inspect the message. - Delete: The infected email is permanently deleted without delivery or notification. Use this option with caution as the email cannot be recovered. ### Antivirus License - Subscription date: Displays the expiration date of the current antivirus signature subscription. - Order extension: Opens the subscription renewal process to extend antivirus signature updates. - Current signatures: Shows the version and date of the currently installed virus signature database. --- ## POPcon Help - Archiving Source: https://www.servolutions.com/popcon/help/archive Language: en ### Archiving ### Enable Archiving Activates email archiving. When enabled, POPcon saves a copy of every downloaded email to the configured archive location before delivering it to Exchange. ### Archive Organization Select how archived emails are organized into folders: - All in one folder: All archived emails are stored in a single directory regardless of date or account. - Per day: Archived emails are organized into subdirectories by date (e.g., 2026-04-12 ). - Per month: Archived emails are organized into subdirectories by month (e.g., 2026-04 ). - Per account: Archived emails are organized into subdirectories named after the source POP3/IMAP account. ### Archive Root Folder Specify the file system path where archived emails are stored. Ensure the POPcon service account has write permissions to this location. ### Exclude [SPAM] Tagged Emails When enabled, emails whose subject line has been tagged with [SPAM] by the antispam module are excluded from the archive. This reduces archive storage consumption by omitting unwanted messages. --- ## POPcon Exchange Server Settings — Address, Port, StartTLS Source: https://www.servolutions.com/popcon/help/exchange Language: en ### Exchange Server Configuration ### Exchange Server Address The hostname or IP address of the Microsoft Exchange Server that POPcon delivers emails to via SMTP (e.g., exchange.local or 127.0.0.1 ). ### IP Port The SMTP port on the Exchange Server. Default is 25 . Change this if your Exchange Server uses a non-standard SMTP receive connector port. ### Allow StartTLS When enabled, POPcon attempts to upgrade the SMTP connection to Exchange using StartTLS encryption. The Exchange Server must have a valid certificate and support the STARTTLS command. ### Timeout Maximum time in seconds to wait for a response from the Exchange Server during SMTP delivery. Increase this value if you experience timeouts with large emails or a slow network connection. ### Retry Interval Time in seconds to wait before retrying delivery to the Exchange Server after a failed attempt. ### HELO Domain The domain name POPcon sends in the SMTP HELO/EHLO command when connecting to the Exchange Server. This should match a domain recognized by your Exchange configuration. ### Postmaster Address The email address used as the envelope sender (MAIL FROM) when POPcon delivers emails to Exchange. This address receives non-delivery reports and bounce notifications. ### Notification Options - Spam rejected: Send a notification to the postmaster when an email is rejected by the antispam filter. - Unknown address rejected: Send a notification to the postmaster when an email cannot be delivered because the recipient address does not match any Exchange mailbox. - Moved to BADMAIL: Send a notification to the postmaster when an email is moved to the badmail folder due to a virus detection or repeated delivery failure. ### Test Settings Click this button to verify the SMTP connection to the Exchange Server. POPcon will attempt to connect, authenticate, and send a test HELO/EHLO command to confirm that delivery is possible. --- ## POPcon Help: General Options and Log Files Source: https://www.servolutions.com/popcon/help/general Language: en ### General Options ### License - Status: Displays the current license state — registered, trial, or expired. - Enter Key: Opens the license key entry dialog to activate a purchased license or update an existing key. - Trial Expiry Notification: Shows the number of days remaining in the trial period. After expiration, POPcon continues to operate with reduced functionality until a valid license key is entered. ### Log File Configuration - Single file limited to N lines: POPcon writes all log entries to a single log file and truncates it when it exceeds the configured line limit. Older entries are discarded first. - Daily log files: POPcon creates a new log file each day with the date in the filename (e.g., popcon-2026-04-12.log ). This makes it easier to review activity for specific dates. - Delete logs older than N days: Automatically removes daily log files that are older than the specified number of days to manage disk space. --- ## POPcon Help: Distribution Rules (PRO) Source: https://www.servolutions.com/popcon/help/rules Language: en ### Distribution Rules Distribution rules allow fine-grained control over how emails are routed after download. Rules are evaluated in order from top to bottom; the first matching rule determines the action taken unless processing is configured to continue. ### Rule List Displays all configured distribution rules in their current priority order. Each rule shows its name, conditions summary, and configured action. ### Controls - Add: Opens the Rule Details dialog to create a new distribution rule. - Edit: Opens the Rule Details dialog for the selected rule to modify its conditions and actions. - Remove: Deletes the selected distribution rule. - Move Up: Moves the selected rule higher in the list, increasing its priority. Rules higher in the list are evaluated first. - Move Down: Moves the selected rule lower in the list, decreasing its priority. Rules lower in the list are evaluated after those above them. Rule ordering is critical: because rules are evaluated top-to-bottom, more specific rules should generally be placed above more general ones to ensure correct routing. --- ## POPcon Help - Rule Details Source: https://www.servolutions.com/popcon/help/rules-details Language: en ### Rule Details ### Rule Name A descriptive name for the rule, displayed in the rule list. Use a meaningful name that reflects the rule’s purpose (e.g., “Sales team routing” or “Block known spam sender”). ### IF Conditions Define one or more conditions that an incoming email must match for the rule to apply. ### Condition Criteria Each condition matches against one of the following email properties: - Sender: The From: header address of the email - Recipient: The To: or CC: header address of the email - Subject: Text contained in the Subject: header ### Condition Controls - Add: Add a new condition to the rule. - Edit: Modify an existing condition. - Remove: Delete a condition from the rule. ### Condition Logic - AND: All conditions must match for the rule to apply. - OR: At least one condition must match for the rule to apply. ### THEN Actions Define the action to take when the IF conditions are met: - Route to: Deliver the email to a specified Exchange mailbox address, overriding the default recipient resolution. - Forward copy to: Deliver the email to the original recipient and also send a copy to the specified address. - Delete without notification: Discard the email silently without delivering it or sending a non-delivery report. ### Stop Processing When enabled, no further rules are evaluated after this rule matches. When disabled, subsequent rules in the list continue to be evaluated, allowing multiple rules to act on the same email. By default, stop processing is enabled. --- ## POPcon Version History — Release Notes 2021–2026 Source: https://www.servolutions.com/popcon/history Language: en ### POPcon / POPcon PRO Version History This history applies to both POPcon and POPcon PRO. ### 2026 v4.10.4 (June 07, 2026) — Stability release. Fixes a service start failure that could occur after the 4.10 OAuth migration when the stored token-expiry value was left empty (the token now refreshes on the next poll instead of failing). Adds configuration protection: configuration is written atomically with a .bak copy, and a configuration file that does not parse is no longer allowed to overwrite a working one. No new features or configuration changes. v4.10.3 (May 24, 2026) — OAuth diagnostic improvement. When Microsoft sign-in fails at the token-exchange step, POPcon Admin now shows the AADSTS error code, trace ID and correlation ID directly in the error dialog — a single screenshot is enough context for support to investigate without further back-and-forth. No functional changes for installations that already work. v4.10.0 (May 19, 2026) — Microsoft OAuth modernized: new public-client app registration under Servolutions IP Corporation, no client_secret shipped, PKCE-only. One-time re-authentication required for existing Microsoft OAuth accounts on upgrade. UX: prompt=select_account for multi-mailbox tenants. Proactive token refresh 5 min before expiry. v4.9.14 (April 12, 2026) — Bugfix: OAuth token renewal now continues to work after restart. Improved: Extended logging in internals.log for OAuth events. v4.9.12 (March 27, 2026) — Improved: Added French, Italian, Portuguese and Chinese language translations. Bugfix: Fixed Internationalized Domain Name (IDN) support for Umlauts and similar characters in domain names. v4.9.11 (March 09, 2026) — Installs additional libraries for new version of antivirus update engine. v4.9.9 (March 03, 2026) — Automatically cleans up list of antispam blacklist servers, removing defunct servers and updating names. Diagnostic error logging when antivirus updates don’t work. v4.9.8 (March 02, 2026) — Bugfix: Crashes when loading a config file from a different server with OAuth references. POPconAdmin window position validation. Repaired [SPAM] tag injection function. v4.9.7 (February 27, 2026) — Additional diagnostics for antispam checking. v4.9.6 (February 26, 2026) — Visual C++ Library detection fix for v14+ redistributables. v4.9.5 (January 07, 2026) — Visual C++ Library detection false error fix. New version of email handling libraries integrated. ### 2025 v4.9.4 (October 31, 2025) — New antivirus update process to support new ClamAV updater (PRO). v4.9.2 (July 26, 2025) — OAuth with Microsoft servers: fixed port allocation issue by selecting ports 8080–8084. v4.9.1 (July 17, 2025) — Fixed problem with digital SMIME signatures invalidated by X-Header modification. ### 2024 v4.8.12 (December 07, 2024) — AV-update fixed. Better error messages for multiple SMTP error responses. v4.8.11 (November 21, 2024) — Bugfix: Exchange email address resolution on Windows 2022 servers. Window position fix for POPconAdmin. v4.8.10 (November 21, 2024) — New feature: Sender address for Postmaster notifications now configurable. v4.8.9 (November 20, 2024) — Several small improvements in the archive function. v4.8.8 (November 19, 2024) — Upgraded AV core engine. v4.8.7 (November 01, 2024) — Uses encrypted AV update path for better antivirus update connectivity. v4.8.6 (October 31, 2024) — Bugfix: Antispam blacklist servers used even when found to be non-working. v4.8.5 (October 21, 2024) — POPconAdministrator uses Roaming Profile folder to persist dialog sizes and positions. v4.8.4 (October 17, 2024) — Roaming Profile implementation. Import of old POPcon v3 registry entries made more robust. v4.8.3 (October 02, 2024) — POPconAdministrator persists dialog sizes and positions between sessions. v4.8.2 (October 02, 2024) — New: X-cloud-security-recipient header supported. Retry-folder issues with antivirus software fixed. v4.8.1 (September 23, 2024) — New: OAuth2 modern authentication for both Google and Microsoft accounts. v4.7.18 (August 21, 2024) — Bugfix: Archive folder creation and email copying. v4.7.17 (August 12, 2024) — Removed forced VC++ Redist installation; added warning in Admin instead. v4.7.16 (July 24, 2024) — Better protection against double-download emails left on POP3 server. v4.7.15 (July 16, 2024) — Auto-installs missing VC++ Redist. Less resource-intensive AV implementation. v4.7.14 (July 12, 2024) — Auto-installs missing VC++ Redist. v4.7.11 (June 14, 2024) — New POP3/SMTP library version for extended email header field compatibility. v4.7.10 (June 10, 2024) — Correct error message for IMAP mail download failures. ### 2023 v4.7.9 (May 19, 2023) — VC++ Redistributable package installation. Debug info for .NET and VC++ redist in internals.log. v4.7.8 (May 03, 2023) — Bugfix: Function to silently drop specific recipients. v4.7.7 (May 01, 2023) — Bugfix: Unicode character crashes in subject lines. Archiving with/without SPAM tags. Increased AV system compatibility. v4.7.6 (April 16, 2023) — Bugfix: Missing x64 antivirus files. v4.7.4 (April 13, 2023) — Bugfix: Missing x64 Visual C++ redistributable library. v4.7.3 (April 11, 2023) — Bugfix: Chilkat library startup with x64 version. v4.7.2 (April 07, 2023) — Bugfix: Notification email template preservation for non-transferrable emails. v4.7.1 (April 03, 2023) — Additional log details for internals.log. v4.7.0 (April 02, 2023) — Minor changes to error handling code. ### 2022 v4.6.9 (June 30, 2022) — Timeout extended for POP3 server connections. PRO: Antivirus disabled state now reported correctly. v4.6.8 (June 05, 2022) — Bugfix: Antivirus updates. v4.6.2 (January 26, 2022) — New: X-FORWARDED-FOR header support for catch-all mailbox distribution. v4.6.1 (January 20, 2022) — Bugfix: Antivirus data files update not working on some client installs. ### 2021 v4.5.1 (July 03, 2021) — Multiple bugfixes and improvements: archive exception handling, antispam list sorting, resizable configuration forms, CTRL+A account selection, rule sorting fixes. v4.0 (April 11, 2021) — New: Parallel download of multiple POP3/IMAP mailboxes (PRO). Improved download speed. TLS1.2 encryption support. ### Earlier Versions v3.94 (November 17, 2016) — Long file names in MIME headers now detected correctly for RULES. v3.93 (October 16, 2015) — Timeout problems during email transfer to Exchange 2013 solved. v3.92 (April 20, 2015) — Bugfix: Inefficient memory management for list of emails kept on POP3 servers. v3.91 (April 17, 2015) — Updated to OpenSSL v1.02a library for improved SSL speed and stability. v3.90 (March 25, 2015) — SSL connections speed up by caching connection parameters. v3.89 (March 10, 2015) — New OpenSSL Library v1.02 for faster SSL connections. v3.84 (April 11, 2014) — Using OpenSSL v1.0.1g with ‘Heartbleed’ fix. v3.81 (June 13, 2013) — X-Orig-To header support. ESET antivirus greylisting support with automatic retries. v3.77 (April 20, 2012) — Multiple new features: 0-byte email removal, scanner/fax device support, per-account archiving, 554 error handling. v3.74 (September 30, 2011) — Continuous downloading with 0-minute cycle time. v3.70 (September 08, 2008) — Windows 2008 support. Exchange 2007 extended support. Archive function. v3.60 (December 07, 2006) — Per-mailbox display names. Separate antivirus check pass. X-POPCON-SPAMCHECK header. v3.50 (July 28, 2006) — Lotus Notes Domino variant. Blacklist/whitelist import/export. Read receipt removal. v3.20 (September 19, 2005) — IMAP and IMAP-SSL mailbox support. New antivirus engine. v3.00 (April 22, 2005) — Catch-all function. POP3 over SSL. Regular expression support. v2.91 (February 09, 2004) — User-defined blacklists/whitelists. Rules engine phrase search. v2.80 (August 01, 2002) — Antispam using blacklist-DNS servers (PRO). v1.90 (February 09, 2010) — First published version after beta phase. --- ## POPcon System Requirements — Windows & Exchange Versions Source: https://www.servolutions.com/popcon/requirements Language: en ### POPcon System Requirements ### Operating System Windows 2025 Server™, Windows 2022 Server™, Windows 2019 Server™, Windows 2016 Server™, Windows 2012 Server™ (incl. R2), Windows 2011 SBS Server™, Windows 11™ x86 or x64, Windows 10™ x86 or x64, Windows 8™, Windows 7™ ### Compatible Mail Server Software Exchange Server SE™, Exchange Server 2019™, Exchange Server 2016™, Exchange Server 2013™, Exchange Server 2010™, Exchange Server 2007™, Exchange Server 2003™, Exchange Server 2000™, and all SBS versions of the above. Also compatible with: Lotus Domino/Notes™, Tobit David™, Apple Mac OS Lion Mail Server. Moving to Exchange Server SE? What Microsoft changed, what stays the same for POPcon, and what to check after an in-place upgrade or on a new server is in the guide Exchange Server SE and POP3/IMAP mailbox retrieval . ### Hardware - CPU & Memory: No special requirements - Disk: 10 MB plus the amount needed to temporarily store downloaded emails before they are forwarded to Exchange - Network: One network adapter is sufficient; POPcon also works with two or more cards ### Internet Connection Any internet connection via dial-up or routers, as long as POPcon can connect to POP3 and IMAP ports on your ISP mailbox servers. ### Where to install POPcon can run on the Exchange server itself, on another Windows Server or on a Windows 10/11 machine. What each placement needs — receive connector scope, port 25 path, antivirus exclusions — is in the guide Where to install a POP3/IMAP connector . --- ## POPcon Support — Exchange Setup Guides, FAQ, Contact Source: https://www.servolutions.com/popcon/support Language: en ### POPcon Support Email and phone support is included with all our products. We respond quickly. Contact: support@servolutions.com ### Exchange Server Configuration Guides - Configuration of Exchange 2013 or 2016 Server - Configuration of Exchange 2010 Server (incl. SBS 2011) - Configuration of Exchange 2007 Server (incl. SBS 2008) - Configuration of Exchange 2003 Server - Configuration of Exchange 2000 Server - Configuration of Exchange Server 5.5 ### Frequently Asked Questions The Knowledge Base covers 60+ FAQ articles. Frequently referenced topics: ### Configuration & Authentication - Transfer POPcon settings to a new server - Gmail with OAuth2 (modern authentication) - Microsoft 365 / Outlook online with OAuth2 - Why POPcon needs the “accepted domains” setting - ISA-Server proxy configuration ### Email Delivery Issues - “530 5.7.1 Client was not authenticated” from Exchange - “550 5.7.1 Unable to relay” from Exchange - Exchange does not accept emails larger than 10 MB - Emails to unknown recipients stuck in queue - BCC recipients do not receive the email - Distribution group rejects external emails - IONOS blocks non-delivery reports and out-of-office messages ### Error Resolution - All Exchange SMTP error codes a connector sees, on one page — 421, 451, 452, 503, 530, 550, 552, 554 with cause and fix - “452 4.3.1 Insufficient system resources” - “451 4.7.0 Temporary server error” (Exchange 2013) - “421 4.4.1 Connection timed out” - Connection unexpectedly closed - STARTTLS command error - Port 25 blocked / cannot reach Exchange ### Advanced Topics - How the antispam feature works - Wildcards in the anti-spam blacklist (`*@spammer.com`) - Spam checking is very slow - Mail does not reach mail-enabled public folders - Enable non-delivery reports (NDRs) in Exchange 2003 - Virus scanner deletes .msg files — POPcon hangs - Trigger mail retrieval from command line - Where is the POPcon log file? View full Knowledge Base → --- ## Terms of Service — POPcon Source: https://www.servolutions.com/popcon/termsofservice Language: en ### Terms of Service Applicable to POPcon and POPcon PRO. ### 1. Introduction POPcon and POPcon PRO collect emails from users’ Gmail or Outlook 365 mailboxes and forward them to the SMTP server of the user’s choice, typically Microsoft Exchange. By using these applications, you consent to this agreement. Your use is also governed by Google’s and Microsoft’s terms of service and privacy policies. ### 2. User Eligibility You are responsible for maintaining the confidentiality of your account credentials and for all activities that occur under your account. ### 3. Description of Services POPcon and POPcon PRO collect emails from Gmail and Outlook 365 using their respective APIs and forward them to the user’s SMTP server. Google OAuth: Access to https://mail.google.com/ is requested for email forwarding. Microsoft OAuth: Access to Microsoft API scopes as necessary for email forwarding functionality. ### 4. User Obligations You must comply with all local, state, national, and international laws. You may not use the service for unlawful purposes, interfere with its operations, or circumvent security measures. ### 5. Data Collection and Privacy POPcon and POPcon PRO access email content, metadata, and other relevant user data required to perform the email forwarding service. We strictly adhere to Google’s Limited Use Requirements and Microsoft’s data handling policies. Your data will not be transferred to third parties except where necessary to provide the service. We do not sell user data. Your data is not used for advertising purposes. You may revoke the app’s access to your data at any time through your Google or Microsoft account settings. ### 6. Third-Party Services By using POPcon and POPcon PRO, you agree to Google’s API Services User Data Policy and Microsoft’s APIs Terms of Use. We are not responsible for the practices or performance of Google or Microsoft services. ### 7. Intellectual Property We own all rights to the POPcon and POPcon PRO apps and their content, except for user-provided data. We grant you a limited, non-exclusive, non-transferable license to use the app in accordance with these terms. ### 8. Disclaimers POPcon and POPcon PRO are provided “as is” without any warranties of any kind. Our liability is limited to the maximum extent permitted by law. ### 9. Termination We reserve the right to suspend or terminate your access at any time, with or without cause or notice. ### 10. Data Protection We comply with GDPR for users in the European Economic Area and CCPA for users in California. These apps are not intended for use by children under the age of 13. ### 11. Contact support@servolutions.com © 2000–2026 Servolutions IP Corporation --- ## Pricing — Servolutions Email Infrastructure Software Source: https://www.servolutions.com/pricing Language: en ### Simple, honest pricing On-premise tools are one-time per-server licenses. No per-user fees. No forced renewals. Buy once — use it as long as your infrastructure needs it. 30-day full-featured trial No credit card for trial No reinstall to license On-Premise Products Per-server, one-time license. Prices listed in USD. Flagship ### POPcon ™ POP3 and IMAP retrieval into Exchange Server. Automatic mail distribution, TLS, Windows service. View in Shop - POP3 & IMAP retrieval - TLS 1.2 / 1.3 encryption - Windows service - Exchange 4.5 – 2019 + SE - Per-server license Start 30-day free trial → Advanced ### POPcon PRO ™ Everything in POPcon plus built-in antivirus, antispam, parallel threads, and mail archiving. View in Shop - Everything in POPcon - Built-in antivirus scanning - Built-in antispam filtering - Parallel download threads - Mail archiving Start 30-day free trial → SMTP Routing ### MultiSendcon ™ Route outbound Exchange email through different SMTP smart hosts based on sender address. View in Shop - Unlimited routing rules - Per-sender SMTP credentials - TLS 1.2 / 1.3 support - Exchange 4.5 – 2019 + SE - Lower-priced LITE edition available Start 30-day free trial → ChangeSender™ and AddressView™ — Outlook add-ins priced per-user. See the shop for current pricing. Cloud SaaS ### MailSync Hub Cloud IMAP sync for Microsoft 365 / Exchange Online environments. OAuth 2.0 authentication, hosted on Azure, zero on-premise installation. Subscription-based pricing — contact us for your mailbox volume. Monthly or annual billing Pricing based on mailbox count No on-premise software Azure-hosted, 99.9% uptime SLA Contact Sales Learn More Cloud SaaS Azure-hosted ### Ready to buy? Purchase licenses directly in our online shop. Instant delivery by email. All major credit cards accepted. Go to Shop Try First (Free) --- ## Privacy Policy — Servolutions Source: https://www.servolutions.com/privacy Language: en ### Privacy Policy At Servolutions, we take your privacy seriously. This Privacy Policy explains how we collect, use, and protect your personal information when you interact with our website, place an order, or use our services, including POPcon and POPcon PRO. By using our services, you consent to the information collection practices outlined in this policy. ### 1. Information We Collect Personal Data: We collect your name, email address, mailing address, phone number, and payment information when placing an order. Site visitors may browse anonymously, though personal details are necessary for transactions. Non-Personal Data: We automatically collect browsing data such as browser type and referral source during website visits. ### 2. How We Use Your Information Transaction Processing: Personal data is used to fulfill customer orders and deliver services. This information will not be sold, exchanged, transferred, or provided to any other company without your consent, except as required to provide the requested service. Communications: Email addresses may receive order updates, company announcements, and product information. You may unsubscribe using the instructions in each message. ### 3. How We Protect Your Information - All sensitive data (such as payment information) is encrypted using SSL technology during transmission. - Access to personal information is restricted to authorized personnel with confidentiality obligations. - We do not retain sensitive payment data after a transaction is complete. ### 4. Cookies We use cookies to enhance user experience and understand preferences. You may disable cookies through your browser settings, though this may affect site functionality. This website uses Google Analytics 4, a web analytics service of Google Ireland Limited. IP addresses are anonymised, Google signals and ad personalisation are disabled, and no data is used for advertising. Google may process this data on servers outside the EEA. You can prevent collection with the Google Analytics opt-out browser add-on . ### 5. Third-Party Disclosure We do not sell, trade, or transfer personally identifiable information to third parties, except when working with trusted partners assisting our operations or when legally required. ### 6. GDPR — Your Rights For EEA residents, you have the right to access, correct, or delete your personal data; restrict or object to processing; request data portability; and object to marketing. Contact us to exercise these rights. ### 7. Children In compliance with COPPA, we do not collect information from individuals under the age of 13. ### 8. Changes to This Policy We reserve the right to update this Privacy Policy at any time. Significant changes will be communicated by email or website notice. ### 9. Contact Servolutions IP Corporation 8 The Green STE R, Dover, DE 19901, United States Phone: +1 (302) 857-0301 European contact: Servolutions GmbH, Castleyard OfficePods 14, 20-21 St. Patricks Road, A96D573 Dalkey, Ireland, Phone: +49 40 209338822 Email: info@servolutions.de --- ## Site Index — Servolutions Source: https://www.servolutions.com/sitemap Language: en ### Site Index ### Main Pages - Home - About Servolutions - Downloads - Freeware Utilities ### POPcon - POPcon Overview - Features - Download - System Requirements - Version History - Support ### POPcon PRO - POPcon PRO Overview - Features - Download - System Requirements - Support ### ChangeSender - ChangeSender Overview - Features - Download - Installation Guide - System Requirements - Version History - Support ### MultiSendcon - MultiSendcon Overview - Download - Installation Guide - System Requirements - Version History - Support ### AddressView - AddressView Overview - Download - System Requirements - Support ### Support - Support Overview - Knowledge Base - Exchange 2013/2016 Configuration - Exchange 2010 Configuration - Exchange 2007 Configuration - Exchange 2003 Configuration - Exchange 2000 Configuration - Exchange 5.5 Configuration ### Legal - Privacy Policy - Disclaimer --- ## Servolutions Support — Contact by Email or Phone Source: https://www.servolutions.com/support Language: en Support ### We're here to help For technical support, licensing questions, or general enquiries — reach us directly. No ticket queue, no scripted responses. Contact Support Email directly Email: support@servolutions.com · Phone: +1 (302) 857-0301 Looking for an answer first? Try the knowledge base or the Exchange mail flow guides . --- ## 530 SMTP authentication is required — Exchange/POPcon fix Source: https://www.servolutions.com/support/articles/530SMTPauthenticationisre Language: en ← Knowledge Base ### "530 SMTP authentication is required" — what does this mean? This error does not come from Exchange — it comes from another mail server (typically hMailServer or a similar SMTP server) that is running on the same machine as POPcon and is listening on port 25. POPcon connects to whatever answers on port 25 at the configured address, and if that is hMailServer or another authenticated mail server, it will receive this rejection. ### Fix options - Remove the conflicting mail server if it is not needed. - Change the port — move the conflicting server to a different port, and configure POPcon's Exchange delivery port to match (set on the EXCHANGE configuration tab in POPcon). Need more help? Contact support --- ## POPconAdmin does not work or cannot communicate with the POPcon service — Servolutions Support Source: https://www.servolutions.com/support/articles/adminonlyexit Language: en ← Knowledge Base ### POPconAdmin does not work or cannot communicate with the POPcon service POPconAdmin communicates with the POPcon service over TCP ports 22772–22774. Troubleshooting steps: - Make sure only one instance of POPconAdmin is running. - Open ports 22772, 22773, 22774 in the Windows firewall on the POPcon server. - If running POPconAdmin on a different machine, ensure those ports are open between the machines. - Verify POPcon is running as a service (check Windows Services). ### Alternative: direct configuration If POPconAdmin cannot connect, you can configure POPcon directly: - Stop the POPcon service. - Run POPconSrv.exe from the program folder — it opens a maintenance menu. - Edit configuration, then restart the service. Need more help? Contact support --- ## All emails are suddenly tagged as SPAM after working fine for a long time — Servolutions Support Source: https://www.servolutions.com/support/articles/allspam Language: en ← Knowledge Base ### All emails are suddenly tagged as SPAM after working fine for a long time This is usually caused by a DNS configuration problem that makes every antispam blacklist lookup return a positive result. ### Diagnosis Open a command prompt and test a known-clean IP against a blacklist: ping 2.0.0.127.bl.spamcop.net This should return IP 127.0.0.2 . If it returns anything else, or if the test for a known-bad IP also succeeds, DNS is behaving incorrectly. ### Fix Check your network adapter's TCP/IP DNS settings. Some routers or ISP configurations append domain suffixes to DNS queries, which breaks blacklist lookups. Remove any extra DNS suffix search entries. Need more help? Contact support --- ## How does the POPcon PRO antispam feature work, and why is it not 100% accurate? — Servolutions Support Source: https://www.servolutions.com/support/articles/antispamhowdoesitwork Language: en ← Knowledge Base ### How does the POPcon PRO antispam feature work, and why is it not 100% accurate? POPcon PRO's antispam feature works by checking the IP address of the sending mail server against internet DNS blacklists (RBLs — Real-time Blackhole Lists). If the IP is listed, the email is tagged as spam. ### Why false positives occur DSL and cable ISPs often share IP address pools. If a residential user on the same IP range sent spam, the entire pool may be blacklisted, affecting legitimate senders on that ISP. ### Why false negatives occur Blacklists react to past abuse. A newly compromised server will not be listed immediately — there is always a lag. Additionally, some spam is sent from legitimate servers (compromised accounts). ### Content filtering limitation Content-based spam detection is inherently imperfect because spammers constantly adapt their techniques to evade filters. Need more help? Contact support --- ## Can POPcon download email from AOL accounts via IMAP? — Servolutions Support Source: https://www.servolutions.com/support/articles/aol Language: en ← Knowledge Base ### Can POPcon download email from AOL accounts via IMAP? Yes. Configure the account as follows: - Server type: IMAP - Server: imap.aol.com - Port: 143 - Username: your AOL username - Password: your AOL password - Delivery: set to forward to a single SMTP address POPcon will download emails from the AOL IMAP inbox and forward them to your Exchange server. ### Screenshot POPcon POP3 configuration for AOL Need more help? Contact support --- ## BCC recipients do not receive the email — TO: and CC: recipients do — Servolutions Support Source: https://www.servolutions.com/support/articles/bcc Language: en ← Knowledge Base ### BCC recipients do not receive the email — TO: and CC: recipients do BCC recipient information is stored in non-standard email headers. POPcon searches for this information in the X-RCPT-TO , X-Original-To , Delivered-To , and other header fields. If BCC delivery is failing, the intermediate mail server (your ISP or the sender's mail system) may have stripped the BCC headers before POPcon received the message. In that case, there is no way for POPcon to determine the BCC recipients. If you believe the headers are present but POPcon is not detecting them, contact support and provide the full email headers for analysis. Why BCC works with individual mailboxes but not always with a catch-all mailbox is explained in the guide Catch-all (multidrop) mailbox vs one POP3 mailbox per user . Need more help? Contact support --- ## "[blacklist] could not be tested and will not be used" — what does this mean? — Servolutions Support Source: https://www.servolutions.com/support/articles/blacklistcouldnotbetested Language: en ← Knowledge Base ### "[blacklist] could not be tested and will not be used" — what does this mean? POPcon runs a self-test on each blacklist server at startup. This error means the blacklist server is returning a positive (spam) result for a known-clean test address. POPcon disables the blacklist to prevent all your mail from being tagged as spam. This is almost always caused by a DNS misconfiguration where your DNS server appends extra suffixes to queries, making unrelated IP addresses appear to be listed. ### Fix Check your network adapter's TCP/IP Advanced DNS settings and remove any extra DNS search suffixes. Then restart POPcon to re-test the blacklists. Need more help? Contact support --- ## Can I use wildcards like `*@spammer.com` in the anti-spam blacklist? — Servolutions Support Source: https://www.servolutions.com/support/articles/blacklistwildcards Language: en ← Knowledge Base ### Can I use wildcards like `*@spammer.com` in the anti-spam blacklist? Short answer: No — the blacklist does not support wildcards or regular expressions. But you do not need them: every entry is matched as a case-insensitive substring of the sender address, so a single short entry can block an entire domain. ### How matching actually works For each incoming message, POPcon PRO takes the sender address, lowercases it, and checks whether any of your blacklist entries appears anywhere inside it. There is no glob expansion, no regex, no special meaning for * , ? or any other character. The exact same logic also applies to Recipient, Subject, Attachment, Header and free-text rules — they all use the same substring engine. ### Concrete examples - Recommended: @spammer.com — blocks every sender from that domain. The leading @ anchors the match at the address boundary, so nicht-spammer.com or info@notspammer.com are not caught by accident. - Does not work: *@spammer.com — the asterisk is treated as a literal character, so only an address that contains the exact six characters *@spam… would match (basically never). - Too loose: spammer.com (no @ ) — this also matches legit.spammer.com.example.org or spammer.computers@othercompany.com . Always include the @ . ### Things to watch for - Case is ignored — @Spammer.COM and @spammer.com behave identically. - Whitespace is NOT trimmed — a trailing space in your entry (e.g. from copy-pasting) will prevent any match. Make sure each entry is clean. ### Bonus tip: clean up old "Display Name " entries Older blacklists often contain pasted full From-lines such as Max Mustermann . These only match when the exact same display name is reused — the moment the same spammer changes it to Marketing Team , the entry no longer fires. Replacing every variant of those entries with a single @spammer.com line both speeds up the lookup (one entry instead of many) and dramatically improves the catch rate, because any sender at that domain will now be blocked regardless of the display name. The same advice applies to a 3000-entry list: collapsing per-sender entries into per-domain entries usually shrinks the list by an order of magnitude with no loss in coverage. Need more help? Contact support --- ## Configuring POPcon for a branch office that handles only part of a domain — Servolutions Support Source: https://www.servolutions.com/support/articles/branchoffice Language: en ← Knowledge Base ### Configuring POPcon for a branch office that handles only part of a domain In a branch office scenario, the branch Exchange server handles a subset of the company's email addresses while the main office handles the rest. ### Configuration - Configure Exchange at the branch to accept an internal domain (e.g. branchoffice.local ) separate from the main company domain. - Assign branch users two SMTP addresses : one in the company domain (e.g. jane@company.com , set as the default reply-to) and one in the internal domain (e.g. jane@branchoffice.local ). - In POPcon's catch-all mailbox settings, enable "Auto replacement of recipient domains" to replace incoming @company.com addresses with @branchoffice.local . This way POPcon routes incoming email to the correct local Exchange mailboxes. Need more help? Contact support --- ## How to disable the ChangeSender add-in for all users in a terminal server / Citrix environment — Servolutions Support Source: https://www.servolutions.com/support/articles/ChangeSenderdisabletermin Language: en ← Knowledge Base ### How to disable the ChangeSender add-in for all users in a terminal server / Citrix environment The ChangeSender client installation includes a utility called ChangeSenderDisable.exe , found in C:\Program Files\Servolutions\ChangeSender . ### Disable for all users - Launch ChangeSenderDisable.exe . - Uncheck "Enable ChangeSender for all users by default" . The add-in remains installed but is disabled for every user on the system. ### Re-enable for specific users - Log in as that user and open Outlook. - Go to Options > Add-Ins > Add-In Options Dialog . - Select ChangeSender and click "Configure ChangeSender" . - Uncheck "Hide/disable Add-In at startup" . ChangeSender will now appear for that user with full send-as functionality. Need more help? Contact support --- ## ChangeSender is installed but the sender address is not changing — Servolutions Support Source: https://www.servolutions.com/support/articles/Changesenderinstalledbutn Language: en ← Knowledge Base ### ChangeSender is installed but the sender address is not changing ChangeSender consists of two components that must both be installed: - Server component — installed on the Exchange server - Client component (Outlook add-in) — installed on each user's PC The Outlook add-in alone is not sufficient. If only the client is installed, ChangeSender appears to work but cannot change the sender address because there is no server component to handle the Exchange-side processing. Install the server component on your Exchange server and the problem will be resolved. See the installation guide for step-by-step instructions. Need more help? Contact support --- ## How to enable non-delivery reports (NDRs) for external senders in Exchange 2003 — Servolutions Support Source: https://www.servolutions.com/support/articles/config_ndr Language: en ← Knowledge Base ### How to enable non-delivery reports (NDRs) for external senders in Exchange 2003 - Open Exchange System Manager. - Go to Global Settings > Internet Message Formats . - Double-click the default entry. - Check "Allow non-delivery reports" . - Click OK. External senders will now receive bounce messages when email cannot be delivered to a recipient on your Exchange server. ### Screenshots — step by step Exchange System Manager Check or uncheck "Allow non-delivery reports". Need more help? Contact support --- ## Exchange SMTP connection unexpectedly closed, or "454 5.7.3 Client does not have permission to submit mail" — Servolutions Support Source: https://www.servolutions.com/support/articles/connectionclosed Language: en ← Knowledge Base ### Exchange SMTP connection unexpectedly closed, or "454 5.7.3 Client does not have permission to submit mail" ### Exchange 2007: SMTP service conflict If the Windows "Simple Mail Transfer Protocol (SMTP)" service is running, it conflicts with Exchange on port 25. Disable and stop this Windows service. ### Exchange 2007: Antispam blocking Add the POPcon server's IP address to the IP Allow List in Exchange antispam settings, and disable the antispam agent temporarily for testing. ### Exchange 2003: Message filtering Disable sender filtering, recipient filtering, and intelligent message filtering in Exchange System Manager. ### General: Firewall / antivirus Configure firewalls or antivirus products to silently drop blocked emails rather than closing the TCP connection — an abrupt connection close looks like an error to POPcon. ### Screenshots — step by step Exchange 2003: The most common cause is sender, recipient or intelligent filtering turned on in Exchange. Check these configuration pages in the Exchange System Manager Ensure that the "Drop connection if address matches filter" option is turned off The connection filter configuration should be empty And the recipient filtering option should be turned off (ensure that "Filter recipients..." is not activated) Intelligent Message Filtering tab • You will find the settings for the SMTP server under Servers/Protocols/SMTP/Default SMTP Virtual Server. Open the properties by right-clicking on the Default SMTP Virtual Server and choosing "Properties" • The settings on tab “General” can normally be left to the defaults. • On the tab "Access" you can find some configuration settings that might interfere with POPcon. • POPcon only works with a standard SMTP connection WITHOUT authentication, so allow "Anonymous access" in the "Authentication" dialog Need more help? Contact support --- ## 421 4.4.1 Connection Timed Out from Exchange 2007 Source: https://www.servolutions.com/support/articles/connectiontimedout Language: en ← Knowledge Base ### "421 4.4.1 Connection timed out" from Exchange 2007 Exchange closed the SMTP connection before POPcon finished transmitting the message. This usually happens with very large messages or a slow network. ### Fix Increase the connection timeout on the Exchange receive connector using the Exchange Management Shell: Set-ReceiveConnector -id "*default*" -ConnectionTimeout 01:00:00 Then restart the Microsoft Exchange Transport service for the change to take effect. Need more help? Contact support --- ## "Mail transfer to Exchange failed: Connection to host denied" — Servolutions Support Source: https://www.servolutions.com/support/articles/connectiontohostdenied Language: en ← Knowledge Base ### "Mail transfer to Exchange failed: Connection to host denied" Exchange's SMTP service is not responding on port 25. Common causes: - Antivirus blocking port 25 — some endpoint security products intercept SMTP. Try disabling temporarily. - Port changed — another application may have claimed port 25. - POPcon lacks connection permission — verify the receive connector allows the POPcon IP address. - Antispam rejecting connection — add the POPcon server's IP to the Exchange IP Allow List. ### Test with TELNET telnet exchangeservername 25 You should see an SMTP banner ( 220 ... ). If the connection is refused or times out, port 25 is blocked between the two machines. ### Screenshots — step by step The computer where POPcon is installed on might not be allowed to connect to the SMTP server of Exchange. Check the settings under Exchange System Manager, Servers, your server, protocols, SMTP, properties of the Virtual Defaultserver for SMTP, Access, Connection. It could also be the antispam portion of any antivirus software installed on the server. Most antivirus packages nowadays include antispam features you might not even be aware of. In the Symantec mail security product for example you need to uncheck the rejection options here Need more help? Contact support --- ## I installed CSCatchAll and configured a catch-all account but it does not seem to work at all! What can I check? — Servolutions Support Source: https://www.servolutions.com/support/articles/cscatchalldoesnothing Language: en ← Knowledge Base ### I installed CSCatchAll and configured a catch-all account but it does not seem to work at all! What can I check? The most common problem is a switched-on Exchange "Recipient Filtering" option. You can find the setting in Exchange System Manager > Global Settings > Properties of "Message Delivery" > Recipient Filtering. Uncheck the "Filter recipients who are not in the Directory". Unfortunatly the recipient filtering takes place before emails reach CSCatchAll and can be re-routed to the correct recipient. If this is not the problem in your case please check the CSCatchAll log file in c:\program files\CSCatchAll\csca.log. You can also send us part of the log with a description of the problem to support@servolutions.com for us to analyse. Need more help? Contact support --- ## Windows Data Execution Prevention (DEP) is crashing the POPcon antivirus engine — Servolutions Support Source: https://www.servolutions.com/support/articles/data_execution_prevention Language: en ← Knowledge Base ### Windows Data Execution Prevention (DEP) is crashing the POPcon antivirus engine Windows DEP monitors program memory usage and can interfere with the antivirus scanning engine in POPcon PRO. ### Fix - Open Control Panel > System > Advanced . - Under Performance, click Settings . - Go to the Data Execution Prevention tab. - Select "Turn on DEP for essential Windows programs and services only" . - Click OK and restart the server. ### Screenshots — step by step Open up Control Panel > System > Advanced Choose Performance Settings and then go to "Data Execution Prevention" Need more help? Contact support --- ## Remove emails stuck in POPcon's delivery queue Source: https://www.servolutions.com/support/articles/deleteamail Language: en ← Knowledge Base ### How to get rid of emails stuck in POPcon's delivery queue Stuck emails are stored as .msg files in the POPcon program folder ( C:\Program Files (x86)\POPcon ). ### To delete Stop the POPcon service, delete the unwanted .msg files, then restart the service. ### To retry delivery Move the .msg files into the PICKUP subfolder. POPcon will attempt delivery again on the next cycle. Need more help? Contact support --- ## How to diagnose malfunctioning antispam blacklist server lookups — Servolutions Support Source: https://www.servolutions.com/support/articles/diagnosespamservers Language: en ← Knowledge Base ### How to diagnose malfunctioning antispam blacklist server lookups Antispam blacklist lookups work by reversing an IP address and querying a DNS blacklist. You can test this manually: ### Test in a CMD window To test SpamCop blacklist: ping 1.1.168.192.bl.spamcop.net This should fail (no response) because 192.168.1.1 is a private address not on the blacklist. ping 2.0.0.127.bl.spamcop.net This should succeed and return 127.0.0.2 because 127.0.0.2 is a test address that is always listed. If the first ping succeeds or the second ping fails, there is a DNS problem — typically extra domain suffixes being appended to queries. Fix your network adapter DNS suffix settings. Need more help? Contact support --- ## Exchange distribution group rejects external senders — fix Source: https://www.servolutions.com/support/articles/distributiongrouprejectse Language: en ← Knowledge Base ### Why does my distribution group not accept emails from external senders? By default, Exchange distribution groups require senders to be authenticated (i.e. internal Exchange users). External senders — including emails forwarded by POPcon — are rejected. ### Fix ### Option A: Exchange Management Console - Open the distribution group properties. - Go to Mail Flow Settings > Message Delivery Restrictions . - Uncheck "Require that all senders are authenticated" . ### Option B: Exchange Management Shell Set-DistributionGroup GROUPNAME -RequireSenderAuthenticationEnabled $False ### Screenshots — step by step Exchange 2010 Management console Distribution Group Exchange 2010 Distribution Group mail flow settings Exchange 2010 Distribution Group delivery restrictions Need more help? Contact support --- ## POPcon Downloads Mail but Cannot Reach Exchange — Fix Source: https://www.servolutions.com/support/articles/downloadbutnofwd Language: en ← Knowledge Base ### POPcon downloads email fine but cannot reach my Exchange server POPcon successfully downloads from your POP3/IMAP server but fails to deliver to Exchange via SMTP. Troubleshooting steps: - Verify the Exchange server address — use the server's network name (e.g. exchangeserver ), not the internet domain. - Verify Exchange services are running — check that "Microsoft Exchange Transport" service is started. - Test with PING — run ping exchangeserver from the POPcon machine to confirm network connectivity. - Test SMTP port 25 — run telnet exchangeserver 25 . You should see an SMTP banner. If not, port 25 is blocked. - Check firewall rules — ensure port 25 is open between the POPcon machine and Exchange. - Check antivirus / antispam — some endpoint security products intercept or block outbound SMTP. Try disabling temporarily to test. - Check the receive connector — verify the POPcon machine's IP address is allowed to connect (see Exchange receive connector settings). The complete setup from accepted domain to first test, including the receive connector settings this article refers to, is in the guide How to download POP3 and IMAP mailboxes into Exchange 2016, 2019 and SE . Which of these checks matter at which placement of the connector — on the Exchange server, a member server or a workstation — is in Where to install a POP3/IMAP connector . Need more help? Contact support --- ## POPcon says it "drops copies" of downloaded email — what does this mean? — Servolutions Support Source: https://www.servolutions.com/support/articles/droppedcopy Language: en ← Knowledge Base ### POPcon says it "drops copies" of downloaded email — what does this mean? This is normal duplicate-prevention behaviour, not an error . When multiple recipients of the same email all share one catch-all POP3 mailbox, POPcon receives multiple copies of that message. POPcon compares the message ID and recipient address — if it detects it has already delivered this message to this recipient, it drops the duplicate copy. No email is lost. The original is delivered; only exact duplicates are dropped. Need more help? Contact support --- ## Does POPcon work with Exchange 2010, 2007, 2003, 2000, 5.5, SBS editions? — Servolutions Support Source: https://www.servolutions.com/support/articles/ex2000 Language: en ← Knowledge Base ### Does POPcon work with Exchange 2010, 2007, 2003, 2000, 5.5, SBS editions? Yes. POPcon uses standard SMTP to deliver mail to Exchange, which makes it compatible with all Exchange versions including: - Exchange 2016 / 2013 / 2010 / 2007 / 2003 / 2000 / 5.5 - All SBS (Small Business Server) editions - Lotus Notes - Tobit David - Any other mail server that accepts standard SMTP on port 25 POPcon does not use Exchange-specific APIs — it communicates via SMTP, so version upgrades do not affect POPcon's compatibility. Background: Does Exchange Server have a built-in POP3 connector? — why the SBS POP3 Connector did not survive the move to standalone Exchange. Need more help? Contact support --- ## "530 5.7.1 Client was not authenticated" error from Exchange — Servolutions Support Source: https://www.servolutions.com/support/articles/exchange2007clientnotauth Language: en ← Knowledge Base ### "530 5.7.1 Client was not authenticated" error from Exchange This error means Exchange is requiring SMTP authentication, but POPcon uses standard unauthenticated SMTP to deliver mail to Exchange. The fix is to allow anonymous connections on the receive connector. ### Exchange 2007 / 2010 / 2013 / 2016 - Open the Exchange Management Console (or Exchange Admin Center). - Navigate to Server Configuration > Hub Transport > Receive Connectors (or Mail Flow > Receive Connectors ). - Open the "Default [SERVERNAME]" or "Default Frontend [SERVERNAME]" connector. - On the Permission Groups tab, check "Anonymous users" . - Click OK and test again. Note: Do not use authenticated SMTP to get around this error. With authentication, Exchange shows every email delivered this way as sent by the account that logged in. The receive connector must permit anonymous connections from the POPcon server's IP address, as described in the Exchange configuration guide . ### Screenshots — step by step Exchange 2007 Receive Connectors Exchange 2007 Receive Connector Permission Groups Need more help? Contact support --- ## Exchange does not accept emails larger than 10 MB — how to increase the limit — Servolutions Support Source: https://www.servolutions.com/support/articles/exchange2007sizelimit Language: en ← Knowledge Base ### Exchange does not accept emails larger than 10 MB — how to increase the limit Exchange receive connectors have a default maximum message size of 10 MB (10240 KB). Increase this as follows: ### Exchange Management Console (2007 / 2010) - Go to Server Configuration > Hub Transport > Receive Connectors . - Open the default receive connector. - On the General tab, increase Maximum message size from 10240 KB to your desired limit (e.g. 102400 for 100 MB). ### Exchange Management Shell set-receiveconnector "*default*" -maxmessagesize 100MB You may also need to increase the limit at the organization level: Organization Configuration > Hub Transport > Global Settings > Transport Settings . The limits of current Exchange versions (2016, 2019, SE) with Microsoft's default values, and what happens to a message at each of them, are in the guide Messages over 10 MB are not arriving: size limits between the POP3 connector and Exchange . ### Screenshots — step by step Exchange 2007 Receive Connectors Exchange 2007/2010 receive connector properties Need more help? Contact support --- ## "550 5.7.1 Unable to relay" error from Exchange — Servolutions Support Source: https://www.servolutions.com/support/articles/exchange2007unabletorelay Language: en ← Knowledge Base ### "550 5.7.1 Unable to relay" error from Exchange This error means your internet domain has not been added to Exchange's list of accepted domains. Exchange rejects delivery for any domain it does not own. What Exchange checks before it answers, and what to do when a host really has to relay to external recipients, is explained in the guide 550 5.7.1 Unable to relay when a connector submits to Exchange . ### Exchange 2007 / 2010 / 2013 / 2016 - Open the Exchange Management Console / Admin Center. - Navigate to Organization Configuration > Hub Transport > Accepted Domains (or Mail Flow > Accepted Domains ). - Click New Accepted Domain . - Enter your internet domain name (e.g. yourcompany.com ) and select Authoritative Domain . - Click Finish and retry. ### Exchange 2003 Add your domain to the Default Policy under Recipients > Recipient Policies in Exchange System Manager. ### Screenshots — step by step Exchange 2007 Accepted Domains List Exchange 2007 new accepted domains Need more help? Contact support --- ## "Exchange aborted receiving the message after N bytes" error — Servolutions Support Source: https://www.servolutions.com/support/articles/Exchangeabortedreceivingt Language: en ← Knowledge Base ### "Exchange aborted receiving the message after N bytes" error Exchange's antispam feature interrupted message receipt mid-transfer. This typically means Exchange detected the sending IP (the POPcon server) as suspicious. ### Fix - Add the POPcon server's IP address to the IP Allow List in Exchange antispam settings. - In Exchange Management Console, go to Server Configuration > Hub Transport > Anti-Spam . - Select IP Allow List and add the POPcon server's IP. Alternatively, disable individual antispam agents one by one to identify which one is causing the abort. Need more help? Contact support --- ## How to forward some accounts to a non-local mailbox on the internet — Servolutions Support Source: https://www.servolutions.com/support/articles/forward_to_internet Language: en ← Knowledge Base ### How to forward some accounts to a non-local mailbox on the internet POPcon delivers to Exchange via SMTP. To forward an address to an external internet mailbox, create a Mail Contact in Exchange that points to the external address, then use that contact's local address in POPcon. ### Exchange 2007 / 2010 / 2013 - In Exchange Management Console, go to Recipient Configuration > Mail Contact . - Create a new Mail Contact with the external email address. - In POPcon, configure the account to deliver to the contact's local Exchange address. ### Exchange 2003 Use Active Directory Users and Computers to create a Contact with an external SMTP address. Use the contact's local address in POPcon. ### Screenshots — step by step Creating a new contact Creating a new contact Creating a new contact Enter the external Email address that you want emails forwarded to Creating a new contact Creating a new contact Creating a new contact Change option Use MAPI rich text format to NEVER. And check the local address (in my case it's the @servolutions.com address on the E-Mail addresses tab. You can add your own local address there if it wasn't created automaitcally. Creating a new contact in AD users and computers Add contact details Enter the EXTERNAL mail address on the internet where the email should get forwarded to Enter the EXTERNAL mail address on the internet where the email should get forwarded to Enter the EXTERNAL mail address on the internet where the email should get forwarded to Enter the EXTERNAL mail address on the internet where the email should get forwarded to Finish the new contact wizard and open up the properties of the newly created contact Go to the E-mail Addresses tab and chose "New", then select "SMTP Address" Enter a new INTERNAL address in your own domain like all the other addresses that POPcon can already forward to Enter a new INTERNAL address in your own domain like all the other addresses that POPcon can already forward to Need more help? Contact support --- ## POPcon delivers email to both the real recipient AND a catch-all mailbox name — Servolutions Support Source: https://www.servolutions.com/support/articles/forwardtocatchall Language: en ← Knowledge Base ### POPcon delivers email to both the real recipient AND a catch-all mailbox name This happens when the catch-all mailbox address at your ISP also appears as a recipient header in incoming emails. POPcon correctly identifies both the real recipient and the catch-all address, delivering to both. ### Fix In POPcon's Advanced configuration page, use the "Remove string from start of recipient addresses" feature. Enter the catch-all mailbox name (e.g. catchall ). POPcon will strip this prefix before matching recipients, preventing duplicate delivery. Need more help? Contact support --- ## Can POPcon download email from Gmail accounts? — Servolutions Support Source: https://www.servolutions.com/support/articles/gmail Language: en ← Knowledge Base ### Can POPcon download email from Gmail accounts? Yes. For accounts using a password (legacy access — may need to enable "Less secure app access" or use an App Password in Google): - Server type: POP3-SSL - Server: pop.gmail.com - Port: 995 - Username: full Gmail address - Password: Gmail password or App Password For modern authentication (recommended): Use IMAP with OAuth2 instead. See the Gmail OAuth2 guide for step-by-step instructions, and the guide Fetching Gmail and Google Workspace mail into Exchange over IMAP with OAuth2 for what Google changed and when. ### Screenshot POPcon POP3 configuration for Gmail Need more help? Contact support --- ## How to connect to Gmail with modern authentication / OAuth2 — Servolutions Support Source: https://www.servolutions.com/support/articles/gmailwithoauth2 Language: en ← Knowledge Base ### How to connect to Gmail with modern authentication / OAuth2 Google requires OAuth2 (modern authentication) for Gmail access. Here is the step-by-step process: - In POPcon, add a new mailbox account. Set the server type to IMAP , server address imap.gmail.com , port 993 . - Click the "Connect OAuth2" button next to the authentication field. - A browser window opens. Sign in to your Google account. - Grant POPcon permission to access your Gmail. - If Google shows an "unverified app" warning, click Advanced and then "Go to POPcon (unsafe)" to proceed. - Complete the authentication flow. - Back in POPcon, the status should show "Authenticated" . - Click "Test access" to verify the connection works. You do not need to enter a password when using OAuth2. The OAuth token is stored securely and refreshed automatically. Background — what Google switched off for Google Workspace and personal accounts, why an app password is not the answer, and IMAP vs POP3 at Google — is in the guide Fetching Gmail and Google Workspace mail into Exchange over IMAP with OAuth2 . ### Screenshots — step by step Note: The IP port number for Gmail IMAP with OAuth is 993, as shown below. Click on the Connect OAuth2 button to begin the OAuth authentication process. A web browser window will open, asking you to sign in with your Google account. Choose the Google account you want to authenticate with. Make sure to select the correct email account. Gmail will ask for permission to allow POPcon email forwarding to read, compose, and delete emails from your Gmail account. Select the checkbox to grant these permissions, and then click Continue. Google will display the requested permissions again, explaining what POPcon email forwarding will be able to do. Click Continue to proceed. Since POPcon is still undergoing Google’s verification process, you may see a warning stating that the app has not been verified. Click on Advanced and proceed by clicking Go to POPcon email forwarding (unsafe) to continue. Once the OAuth authentication is complete, you will see a confirmation message. You can close the browser window and return to POPcon. After authentication, the status in POPcon will show as Authenticated. You can now test the email account connection by clicking on the Test access button to ensure that everything is configured correctly. POPcon will test the connection to Gmail. If the test passes successfully, you are all set to retrieve emails from Gmail using OAuth authentication. Need more help? Contact support --- ## POPcon hangs when my virus scanner deletes infected .msg files — Servolutions Support Source: https://www.servolutions.com/support/articles/hangwhenvirusmsgdel Language: en ← Knowledge Base ### POPcon hangs when my virus scanner deletes infected .msg files Fixed in POPcon version 2.8 and later. POPcon now sends a postmaster notification when a message file disappears unexpectedly, instead of hanging. ### Recommendation Exclude the POPcon program folder ( C:\Program Files (x86)\POPcon ) from real-time antivirus scanning. POPcon processes files very quickly — real-time scanning can interfere with file operations. Schedule a periodic scan instead. Need more help? Contact support --- ## "552 5.3.4 Header size exceeds fixed maximum size" from Exchange — Servolutions Support Source: https://www.servolutions.com/support/articles/Headersizeexeceedsfixedma Language: en ← Knowledge Base ### "552 5.3.4 Header size exceeds fixed maximum size" from Exchange Emails with very long header sections (typically from mailing lists, forwarding chains, or automated systems) are rejected by Exchange because they exceed the default header size limit. ### Fix Increase the maximum header size in Exchange Management Shell: set-receiveconnector -identity Default* -MaxHeaderSize 256kb Then move any affected emails from the BADMAIL folder to PICKUP to retry delivery. Need more help? Contact support --- ## How do I configure CSCatchAll? The Administrator utility only allows me to enter a license code. — Servolutions Support Source: https://www.servolutions.com/support/articles/howtoconfigurecscatchall Language: en ← Knowledge Base ### How do I configure CSCatchAll? The Administrator utility only allows me to enter a license code. You don't. It may seem strange, but CSCatchAll does not need any configuration at all! But how do you configure the user that will receive the catch-all emails for a given domain? Very easy: Just add the smtp email address "catchall@domainname" to the list of addresses of that user in the active directory. Replace "domainname" with your smtp domain name. Suppose we have a user "John Galt" that should receive the catch-all emails. As you can see below, John currently has the email addresses "john@christensen-software.com" and "johngalt@christensen-software.com" in addition to "webmaster@christensen-software.com". To make John the user receiving all the catch-all emails you just add "catchall@christensen-software.com" to the list of email addresses: Use Administrative Tools > Active Directory Users and Computers and open the properties of the user that should receive the catch-all emails that no regular other user catches. Go to the E-mail Addresses tab. Click on New... to add a new email address and choose "SMTP Address" as the type of email address to add. Enter "catchall@domainname" as address to add. In our case it is "catchall@christensen-software.com", so in your case it will be something like "catchall@yourdomain.com". This is the list of addresses after adding the catchall address. You do not need to restart CSCatchAll or reboot the server. CSCatchall will start routing emails addressed to non-exisiting users to the new catchall user John right away. If you have multiple domains defined in your Exchange Server you can add all of the catchall addresses to one user or distribute them to different users by adding the appropriate catchall@... addresses in the active directory. Need more help? Contact support --- ## Re-download messages left on the POP3 server with POPcon Source: https://www.servolutions.com/support/articles/howtoresend Language: en ← Knowledge Base ### How to resend already-downloaded messages If messages are still on the POP3 server and you want POPcon to download them again: - Stop the POPcon service. - Delete the following files from the POPcon program folder: - msguids.tmp - msguids2.bak - msgids.tmp - msgids2.bak - Restart the POPcon service. POPcon will re-download and re-deliver all messages on the next retrieval cycle. Note: This only works if messages have not been deleted from the POP3 server. If deletion after download is configured, the messages are gone from the server. Need more help? Contact support --- ## How to restrict users' choices for Send-As addresses in ChangeSender — Servolutions Support Source: https://www.servolutions.com/support/articles/howtorestrictuserschoices Language: en ← Knowledge Base ### How to restrict users' choices for Send-As addresses in ChangeSender The ChangeSender Server installation includes a utility called "Configure ChangeSender Client Restrictions" . Use it to control what sender addresses each user can choose in Outlook. ### Configuration options - Default — allow users to choose from email addresses configured in Active Directory - Single address — restrict to one specific address with no user choice - Unrestricted — allow users to send from any address ### For computers in the AD domain The Outlook add-in reads restriction settings directly from Active Directory. Configure in the utility and settings apply automatically. ### For computers outside the AD domain (HTTPS connection) - Set restrictions in the utility for the user. - Click "Export config file" . The file is named after the user's email address (e.g. jane@company.com.cfg ). - Transfer the file to the user's computer and import it in the ChangeSender add-in. What the restricted choice means in Exchange terms — Send As, Send on Behalf or sending from an alias — is explained in the guide Send As vs Send on Behalf vs sending from an alias . Need more help? Contact support --- ## Move POPcon Settings to a New Server (popcon.config) Source: https://www.servolutions.com/support/articles/howtransfer Language: en ← Knowledge Base ### How can I transfer my POPcon configuration settings to a new server? ### POPcon v4.x Configuration is stored in the popcon.config file. Downloaded email UIDs are stored in UIDS_xxxxxxxx.dat files (one per mailbox). Both are located in the POPcon program folder (typically C:\Program Files (x86)\POPcon ). - Install POPcon on the new server. - Stop the POPcon service. - Copy popcon.config and all UIDS_*.dat files from the old server to the same folder on the new server. - Start the POPcon service. ### Older POPcon versions (up to v3.9x) Configuration is stored in the Windows registry. Export the key HKEY_LOCAL_MACHINE\Software\POPcon and all subkeys using REGEDIT on the old server. Import the .reg file on the new server. Note (32-bit to 64-bit migration): If migrating from a 32-bit to a 64-bit Windows installation, edit the .reg file before importing and change all occurrences of /Software/POPcon to /Software/Wow6432Node/POPcon . Need more help? Contact support --- ## 452 4.3.1 Insufficient system resources — Exchange fix Source: https://www.servolutions.com/support/articles/insufficientsystemresourc Language: en ← Knowledge Base ### "452 4.3.1 Insufficient system resources" error from Exchange Exchange generates this error when the available hard disk space on the server falls below 4 GB. Exchange pauses mail acceptance to protect database integrity. ### Solution - Free up disk space on the Exchange server (clear logs, temp files, etc.). - Check the BADMAIL folder in the POPcon program directory — move any .msg files to the PICKUP subfolder to retry delivery once space is available. - Consider using a monitoring tool (e.g. ServerPulse) to alert you before disk space runs critically low. Need more help? Contact support --- ## IONOS blocks non-delivery reports and out-of-office messages — Servolutions Support Source: https://www.servolutions.com/support/articles/IONOSblocksNDRsandOOFs Language: en ← Knowledge Base ### IONOS blocks non-delivery reports and out-of-office messages Since January 2024, IONOS (1&1) rejects emails where the sender address field ( MAIL FROM: ) is empty. NDRs and Out-of-Office messages use an empty sender field as required by the SMTP standard — but IONOS blocks them. ### Solution Use MultiSendcon (the lower-priced Lite version is sufficient) as an outgoing relay between Exchange and IONOS. MultiSendcon can automatically fill in a sender address from the message content or a configured default address, making the messages acceptable to IONOS. This is a workaround for a non-standard restriction imposed by IONOS. The behaviour is not configurable in Exchange or POPcon. Background and the setup for several domains behind one provider: see the guide Using IONOS, Strato or GMX as the smart host for Exchange . Need more help? Contact support --- ## Could Not Reach Exchange SMTP Server — Port 25 Blocked Source: https://www.servolutions.com/support/articles/ipport25blocked Language: en ← Knowledge Base ### "Could not reach Exchange SMTP server — check that IP port 25 is not blocked" POPcon cannot connect to Exchange on port 25. Troubleshooting steps: - Check the POPcon log file — it shows the IP address it is trying to reach. Verify this is the correct Exchange server address. - In Exchange, verify the receive connector's Network tab includes the POPcon server's IP in the allowed addresses. - Confirm the Microsoft Exchange Transport service is running on the Exchange server. - Test connectivity: telnet exchangeservername 25 . You should see a 220 ... banner. - If the telnet fails, port 25 is blocked — check the Windows firewall and any network firewall between the two machines. Need more help? Contact support --- ## How to configure POPcon to work with an ISA Server (proxy) — Servolutions Support Source: https://www.servolutions.com/support/articles/isaserver Language: en ← Knowledge Base ### How to configure POPcon to work with an ISA Server (proxy) If your network uses Microsoft ISA Server as a firewall/proxy, you need to create two packet filter rules to allow POPcon's traffic through. ### Packet filters to create ### POP3 filter (incoming mail retrieval) - Protocol: TCP - Direction: Outbound - Local port: Dynamic - Remote port: 110 (or 995 for POP3-SSL) ### SMTP filter (delivery to Exchange) - Protocol: TCP - Direction: Outbound - Local port: Dynamic - Remote port: 25 Need more help? Contact support --- ## Is there a log of POPcon's actions — where can I find it? — Servolutions Support Source: https://www.servolutions.com/support/articles/logfile Language: en ← Knowledge Base ### Is there a log of POPcon's actions — where can I find it? Yes. POPcon logs all activity to a text file: C:\Program Files (x86)\POPcon\POPconSrv.log Open it with any text editor (Notepad, etc.). The log shows every mail retrieval cycle, each message downloaded, delivery status, and any errors. Log file size and rotation settings are configured on the General tab of the POPcon configuration. Need more help? Contact support --- ## Emails from a mailing list are not distributed correctly — Servolutions Support Source: https://www.servolutions.com/support/articles/mailinglist Language: en ← Knowledge Base ### Emails from a mailing list are not distributed correctly When using a catch-all or multidrop POP3 mailbox, the original recipient addresses may be stripped by the mailing list server before POPcon receives the message. This is an inherent limitation of catch-all mailboxes. ### Solutions - Check email headers: POPcon searches multiple header fields (X-Original-To, Delivered-To, Received, etc.) for recipient information. Review the email headers to see if any recipient field is preserved. - Use individual mailboxes: Set up a dedicated POP3/IMAP mailbox for the mailing list subscription. POPcon will deliver to a single address, avoiding the detection problem entirely. The trade-offs between the two setups are compared in the guide Catch-all (multidrop) mailbox vs one POP3 mailbox per user . Need more help? Contact support --- ## "550 5.7.1 Requested action not taken: message refused" from Exchange — Servolutions Support Source: https://www.servolutions.com/support/articles/messagerefused Language: en ← Knowledge Base ### "550 5.7.1 Requested action not taken: message refused" from Exchange Exchange Intelligent Message Filtering (IMF) is rejecting the message as spam. The fix is to change the action from "Reject" to a non-blocking action. ### Exchange 2003 - Open Exchange System Manager. - Go to Global Settings > Message Delivery Properties . - Click the Intelligent Message Filtering tab. - Under "When blocking messages", change the action to "No Action" or "Delete" (not "Reject"). Choosing "Delete" silently discards spam; "No Action" delivers everything. Either option prevents the SMTP rejection that causes the 550 error. ### Screenshots — step by step Open the Exchange System Manager, Global Settings, Message Delivery, Properties Intelligent Message Filtering tab Need more help? Contact support --- ## 421 4.4.2 Message submission rate exceeded — Exchange fix Source: https://www.servolutions.com/support/articles/messagesubmissionrate Language: en ← Knowledge Base ### "421 4.4.2 Message submission rate for this client has exceeded the configured limit" The MessageRateLimit on an Exchange receive connector is set too low for the volume POPcon is submitting. ### Fix First, find the active connector and its current limit: get-receiveconnector | ft name,messageratelimit Then increase it: set-receiveconnector -identity Default* -MessageRateLimit 200 Re-run the first command to confirm the new value is applied. If uncertain which connector is active, apply the command to each connector shown. Need more help? Contact support --- ## 530 5.7.0 Must Issue a STARTTLS Command First — Exchange Source: https://www.servolutions.com/support/articles/MustissueaSTARTTLScommand Language: en ← Knowledge Base ### "530 5.7.0 Must issue a STARTTLS command first" or similar STARTTLS error from Exchange Exchange is requiring TLS encryption before accepting SMTP commands. POPcon uses plain SMTP without STARTTLS, so the receive connector must be configured to allow unauthenticated, unencrypted connections. ### Fix (Exchange 2013 / 2016) - Open Exchange Admin Center. - Go to Mail Flow > Receive Connectors . - Open the Default Frontend [SERVERNAME] connector. - On the Security tab, ensure "Anonymous users" is checked. - Verify TLS is not required (it should only be offered, not enforced). ### Screenshots — step by step You will find the settings for the SMTP server under Servers/Protocols/SMTP/Default SMTP Virtual Server. Open the properties by right-clicking on the Default SMTP Virtual Server and choosing "Properties" The settings on tab "General" can normally be left to the defaults. On the tab "Access" you can find some configuration settings that might interfere with POPcon. POPcon only works with a standard SMTP connection WITHOUT authentication, so allow "Anonymous access" in the "Authentication" dialog Need more help? Contact support --- ## How to have NDRs sent for emails that are too large instead of moving them to TOOLARGE — Servolutions Support Source: https://www.servolutions.com/support/articles/NDRfortoolargeemails Language: en ← Knowledge Base ### How to have NDRs sent for emails that are too large instead of moving them to TOOLARGE POPcon cannot generate NDRs itself — that must be handled by Exchange. The goal is to have Exchange reject oversized messages (generating an NDR) rather than having POPcon quarantine them. ### Step 1: Increase the receive connector limit In Exchange 2007/2010: Server Configuration > Hub Transport > Receive Connectors. Increase the maximum message size to 100 MB (102400 KB) so the connector does not reject at the wrong level. ### Step 2: Set the organisation limit Organization Configuration > Hub Transport > Global Settings > Transport Settings Properties: set "Maximum receive size" to your desired limit (e.g. 20 MB). When a message exceeds the Transport Settings limit, Exchange automatically sends an NDR to the sender. POPcon's TOOLARGE folder will no longer be used. ### Screenshots — step by step Exchange 2007/2010 Receive Connectors Exchange 2007/2010 receive connector properties Exchange 2007/2010 Global Settings Exchange 2007/2010 Transport Settings Need more help? Contact support --- ## How to have non-delivery reports (NDRs) sent for unknown users — Servolutions Support Source: https://www.servolutions.com/support/articles/NDRforunknownusers Language: en ← Knowledge Base ### How to have non-delivery reports (NDRs) sent for unknown users To receive NDRs when email is sent to an address that does not exist in Exchange: - In POPcon, disable "Re-route email to unknown recipients" . - In Exchange, disable recipient filtering so that unknown recipients are rejected with an NDR rather than silently dropped. ### Exchange 2007 / 2010 Exchange Management Console > Organization Configuration > Hub Transport > Anti-Spam > Recipient Filtering: uncheck "Block messages sent to recipients that do not exist" . ### Exchange 2003 Exchange System Manager > Global Settings > Message Delivery > Recipient Filtering: uncheck "Filter recipients who are not in the Directory" . For Exchange 2016, 2019 and SE, the out-of-office and oversized-mail cases, and the reason a report may be generated and still never reach the sender, see the guide NDRs for external senders behind a POP3 connector . ### Screenshots — step by step Exchange 2010 Organization Configuration, Antispam - click for larger image Exchange 2010 - blockierte Empfänger Message Delivery Properties Exchange 2003 - click for larger image On the "Recipient Filtering" page please uncheck "Filter recipients who are not in the Directory". Exchange System Manager Check "Allow non-delivery reports". Need more help? Contact support --- ## 550 5.5.1 User Unknown / 503 5.5.2 Need Rcpt — Exchange Source: https://www.servolutions.com/support/articles/need_rcpt_user_unknown Language: en ← Knowledge Base ### "550 5.5.1 user unknown" or "503 5.5.2 need Rcpt command" from Exchange ### Exchange 2007 / 2010 / 2013 - Verify your domain is listed in Accepted Domains (Organization Configuration > Hub Transport). - Verify users have the correct email address assigned in Active Directory. - For distribution groups: run Set-DistributionGroup GROUPNAME -RequireSenderAuthenticationEnabled $False to allow external senders. ### Exchange 2003 Disable recipient filtering in Exchange System Manager under Global Settings > Message Delivery > Recipient Filtering . ### Screenshots — step by step Check these configuration pages in the Exchange System Manager On the "Recipient Filtering" page the option should be turned off (ensure that "Filter recipients..." is not activated) Ensure also that the "Drop connection if address matches filter" option is turned off on the "Sender Filtering" page The connection filter configuration should be empty Intelligent Message Filtering tab Need more help? Contact support --- ## POPcon does not install: manual installation method Source: https://www.servolutions.com/support/articles/noinstall Language: en ← Knowledge Base ### POPcon does not install on my machine — alternative installation method If the standard installer fails (permission restrictions, Group Policy, etc.), use this manual installation method: - Install POPcon normally on a temporary/test machine. - Copy the entire C:\Program Files\POPcon folder to the target machine. - Uninstall POPcon from the temporary machine. - On the target machine, run POPconSrv.exe from the copied folder. - In the maintenance menu, select "Install and start service" . - Configure POPcon using POPconAdmin.exe . Need more help? Contact support --- ## All emails get forwarded to the postmaster because they "do not have local recipients" — Servolutions Support Source: https://www.servolutions.com/support/articles/nolocalrecipient Language: en ← Knowledge Base ### All emails get forwarded to the postmaster because they "do not have local recipients" This means POPcon does not recognise your domain as a local domain and cannot match recipients to Exchange users. ### Solution In POPcon's POP3/IMAP configuration, find the "Accepted Recipient Domains" field and add your domain name — without the "@" symbol. For example, enter yourcompany.com , not @yourcompany.com . POPcon uses this list to filter and route recipients correctly to Exchange. ### Screenshot POPcon POP3 properties Need more help? Contact support --- ## "554 5.5.2 No valid recipients" error from Exchange — Servolutions Support Source: https://www.servolutions.com/support/articles/novalidrecipients Language: en ← Knowledge Base ### "554 5.5.2 No valid recipients" error from Exchange Exchange rejects the message because it cannot find any valid recipient in its directory. ### Exchange 2000 / 2003 - Verify your internet domain is added to the Default Policy under Recipients > Recipient Policies in Exchange System Manager. - Verify the POPcon machine has relay rights in the virtual SMTP server connector properties. Also check that user email addresses are properly assigned in Active Directory and that the domain in the recipient address matches the accepted domain in Exchange. Need more help? Contact support --- ## Exchange 2007 only accepts one or a few messages at a time from POPcon — Servolutions Support Source: https://www.servolutions.com/support/articles/onlyacceptsfewmessages Language: en ← Knowledge Base ### Exchange 2007 only accepts one or a few messages at a time from POPcon Exchange 2007 has a default MaxRateLimit on receive connectors that restricts how many messages a single client can submit per minute. POPcon can trigger this limit during a large download. ### Fix Increase the rate limit using the Exchange Management Shell: Set-ReceiveConnector "*default*" -MaxRateLimit 200 Adjust the value as needed. The default is typically 5 messages per minute per client. Need more help? Contact support --- ## "Out of Office" replies go to internal users but not to external internet senders — Servolutions Support Source: https://www.servolutions.com/support/articles/outofoffice Language: en ← Knowledge Base ### "Out of Office" replies go to internal users but not to external internet senders This is not a POPcon issue — it is an Exchange configuration setting. By default, Exchange does not send out-of-office replies to external senders. ### Enable external out-of-office replies ### Exchange 2003 - Open Exchange System Manager. - Go to Global Settings > Internet Message Formats . - Double-click the default entry. - On the Advanced tab, check "Allow out of office responses" . ### Exchange 2007 / 2010 / 2013 Use the Exchange Management Shell: Set-RemoteDomain Default -AllowedOOFType All Need more help? Contact support --- ## Can I trigger mail retrieval from the command line? — Servolutions Support Source: https://www.servolutions.com/support/articles/popcontrigger Language: en ← Knowledge Base ### Can I trigger mail retrieval from the command line? Yes. Use the POPconTrigger utility included with POPcon: popcontrigger SERVERNAME Replace SERVERNAME with the name of the computer running the POPcon service. This triggers an immediate mail retrieval cycle. You can call this from batch files, task schedulers, or any script. It is useful for triggering mail checks on demand rather than waiting for the next scheduled interval. Need more help? Contact support --- ## How to protect Wordpress sites with BotFence — Servolutions Support Source: https://www.servolutions.com/support/articles/Protectwordpresssiteswith Language: en ← Knowledge Base ### How to protect Wordpress sites with BotFence BotFence can monitor hack attempts agains your Wordpress sites as well if they are hosted on the same Windows server. You only need to install and activate the BotFence Wordpress plugin. You'll find the plugin file "Wordpress_plugin_for_BotFence.zip" in the BotFence installation folderto or you can download it here . To use the plugin just login to your Wordpress site as Administrator, then select "Plug-Ins" on the menu on the left side and continue to "Add new" next to the titel "Plug-Ins". On the new page "Add Plugins" please select "Upload Plugin" and find the Wordpress_plugin_for_BotFence.zip file. At last please acivate the newly installed plugin. That's all, no configuration is neccessary. The plugin will immediately start working and will relay any failed login attempts to the BotFence background service for processing. BotFence will block and unblock the IP addresses of attackers as normal. Need more help? Contact support --- ## Mail does not reach mail-enabled public folders — Servolutions Support Source: https://www.servolutions.com/support/articles/publicfolder Language: en ← Knowledge Base ### Mail does not reach mail-enabled public folders This is a permissions issue. Exchange public folders require the "Anonymous" user to have at least Contributor rights in order to receive email from external sources (including POPcon). ### Fix - In Outlook, right-click the public folder and choose Properties . - Go to the Permissions tab. - Click Client Permissions . - Select the Anonymous user and set their role to Contributor . - Click OK. ### Screenshots — step by step Public folder Permissions tab Client permissions of a mail-enabled public folder. Need more help? Contact support --- ## Emails to mail-enabled public folders arrive as "posts" instead of emails — Servolutions Support Source: https://www.servolutions.com/support/articles/publicfolderpostinsteadof Language: en ← Knowledge Base ### Emails to mail-enabled public folders arrive as "posts" instead of emails By default, Exchange stores inbound email to public folders as "posts" (IPM.Post item type). You can change this via a registry setting: - Open Registry Editor ( regedit ) on the Exchange server. - Navigate to: HKEY_LOCAL_MACHINE\System\CurrentControlSet\Services\MSExchangeIS\Public-{GUID} (replace {GUID} with your public folder store GUID). - Create a new DWORD value named Incoming defaults to IPM.Note . - Set the value to 1 to store as email (IPM.Note); set to 0 to store as post (IPM.Post). - Restart the Microsoft Exchange Information Store service. Need more help? Contact support --- ## POPcon moved emails to TOOLARGE or BADMAIL folders — how to resend them — Servolutions Support Source: https://www.servolutions.com/support/articles/retrytransfertoexchange Language: en ← Knowledge Base ### POPcon moved emails to TOOLARGE or BADMAIL folders — how to resend them POPcon moves messages to these subfolders when delivery fails: - TOOLARGE — message exceeds the size limit configured in Exchange. - BADMAIL — delivery failed for another reason. ### To retry - Fix the underlying issue first (e.g. increase the Exchange message size limit). - Move the .msg files from TOOLARGE or BADMAIL into the PICKUP subfolder. - POPcon will pick them up on the next retrieval cycle and attempt delivery again. Need more help? Contact support --- ## How to use the same sender address for two Exchange mailboxes — Servolutions Support Source: https://www.servolutions.com/support/articles/samesenderaddressfortwoma Language: en ← Knowledge Base ### How to use the same sender address for two Exchange mailboxes Exchange does not natively support sharing a sender address between multiple mailboxes. ChangeSender solves this. ### Setup - Install ChangeSender server components on Exchange and the Outlook add-in on all client machines. - In the "Configure ChangeSender Client Restrictions" utility, allow users to send from addresses beyond their own Active Directory entries (choose "Unrestricted" or add the shared address explicitly). - In Outlook, open a new email and click the properties icon next to the sender dropdown. - Add the shared address (e.g. sales@company.com ) as an available option or set it as the default. ### Routing incoming replies To route incoming email for the shared address to multiple recipients, create an Exchange distribution group with that address and add all relevant members. How this compares with Exchange's own Send As and Send on Behalf permissions and with a shared mailbox is covered in the guide How Outlook users can choose a different From address on Exchange on-premises . Need more help? Contact support --- ## How to manually create the MultiSendcon Send Connector in Exchange — Servolutions Support Source: https://www.servolutions.com/support/articles/Sendconnectormanualcreati Language: en ← Knowledge Base ### How to manually create the MultiSendcon Send Connector in Exchange The MultiSendcon installer normally creates a send connector in Exchange automatically. If it fails (e.g. due to permissions or Group Policy restrictions), create it manually using the Exchange Management Shell: new-sendconnector -name MultiSendcon -Addressspaces "SMTP:*;100" -port 2500 -SmarthostAuthMechanism none -smarthosts 127.0.0.1 This creates a connector named "MultiSendcon" that routes all SMTP traffic ( * ) to 127.0.0.1 on port 2500 (the default MultiSendcon listening port) without authentication. After creating the connector, verify it appears in Exchange Management Console under Organization Configuration > Hub Transport > Send Connectors . Change its cost from 100 to 1 to make it the preferred route. Background: Exchange selects a send connector by the recipient domain and the cost, never by the sender, which is why a single connector to MultiSendcon replaces several per-provider connectors. See the guide Exchange send connectors route by recipient domain, not sender . If outgoing mail waits in the Unreachable queue with “A matching connector cannot be found to route the external recipient”, the connector is missing or still disabled: causes and fix . Need more help? Contact support --- ## MultiSendcon service won’t start after upgrading — "ChilkatDotNet47.dll or one of its dependencies could not be found" — Servolutions Support Source: https://www.servolutions.com/support/articles/Servicewontstartafterupgr Language: en ← Knowledge Base ### MultiSendcon service won’t start after upgrading — "ChilkatDotNet47.dll or one of its dependencies could not be found" After upgrading MultiSendcon from an older version (e.g. a 2021-era release) to the current version, the service fails to start. The internals.log file shows an entry like this: Unhandled Exception: The file or assembly "ChilkatDotNet47.dll" or one of its dependencies could not be found. The specified module could not be found. at MultiSendconService.MSCService.UnlockChilkat() at MultiSendconService.Program.Main() (On a German system the message reads: „Die Datei oder Assembly ChilkatDotNet47.dll oder eine Abhängigkeit davon wurde nicht gefunden.“ ) ### Cause The key phrase is "or one of its dependencies" . The ChilkatDotNet47.dll file itself is present in the MultiSendcon program folder — what is missing is a dependency of it. Current versions of MultiSendcon use an updated Chilkat component that is built against the Microsoft Visual C++ 2015–2022 Redistributable (x64) runtime. Older versions used an older Chilkat build that relied on an earlier runtime, which was already installed on the server. After upgrading, the newer runtime is required but is not yet present, so the service cannot load the Chilkat library and stops within a few seconds of starting. ### Solution - Download the latest Microsoft Visual C++ Redistributable (x64) directly from Microsoft. On the Microsoft download page this is the top entry, "Latest supported v14 (for Visual Studio 2017–2022)" → Latest supported Redistributable version . Choose the X64 build ( vc_redist.x64.exe ) — not x86 or ARM64. - Run vc_redist.x64.exe and complete the installation. - Start the MultiSendcon service again, either from the Windows Services console or from a command prompt: sc start MultiSendconService No reinstall of MultiSendcon is required. Once the runtime is present, the Chilkat component loads and the service starts normally. You can confirm success in internals.log — you should see the "Waiting for SMTP connections on …, IP port 2500" line instead of the exception. How to verify it was the runtime: on the affected server, open a command prompt and run where vcruntime140_1.dll . If the file is reported as not found, the Visual C++ runtime was indeed missing — older redistributables (2013 and earlier) do not include this file, which the current Chilkat component requires. For configuring the Exchange send connector that routes mail to MultiSendcon on port 2500, see How to manually create the MultiSendcon Send Connector in Exchange . Need more help? Contact support --- ## What is the shortest mail download interval POPcon supports? — Servolutions Support Source: https://www.servolutions.com/support/articles/shortestdownloadinterval Language: en ← Knowledge Base ### What is the shortest mail download interval POPcon supports? The shortest download interval is 1 minute . If a retrieval cycle takes longer than the configured interval (e.g. you have a 2-minute interval but the cycle takes 3 minutes), POPcon does not overlap cycles. Instead, it starts the next cycle at the next full minute after the current cycle completes. No emails are missed or duplicated. Need more help? Contact support --- ## Only messages under 10 MB come through — does POPcon impose a size limit? — Servolutions Support Source: https://www.servolutions.com/support/articles/sizelimit Language: en ← Knowledge Base ### Only messages under 10 MB come through — does POPcon impose a size limit? POPcon itself handles messages up to 100 MB and beyond — there is no practical size limit in POPcon. The 10 MB restriction is coming from Exchange. Exchange enforces message size limits in three separate locations — all three must be increased: - Receive connector: Server Configuration > Hub Transport > Receive Connectors > default connector > Maximum message size - Organisation-level: Organization Configuration > Hub Transport > Global Settings > Transport Settings > Maximum receive size - Per-mailbox: Each user's mailbox delivery restrictions in Active Directory Users and Computers Use the Exchange Management Shell shortcut: set-receiveconnector "*default*" -maxmessagesize 100MB Which of the limits stops a message, whether the sender is told, and the commands for Exchange 2016, 2019 and SE are explained in the guide Messages over 10 MB are not arriving: size limits between the POP3 connector and Exchange . ### Screenshots — step by step Message size limit on the Exchange Properties of the Virtual Defaultserver for SMTP Message size limit on the Exchange Message Delivery Properties Message size limit on the Active Directory user delivery restrictions Need more help? Contact support --- ## POPcon PRO Spam Check Slow (30 s per Message) — Fix Source: https://www.servolutions.com/support/articles/slowspamcheck Language: en ← Knowledge Base ### Spam checking takes 30 seconds per message — why is it so slow? The antispam feature in POPcon PRO works by querying DNS-based blacklists. If a blacklist server is slow, unreachable, or no longer exists, every message will wait for a DNS timeout before proceeding. ### Common causes - The list.dsbl.org blacklist is no longer operational (shut down). Remove it from your blacklist settings. - Your DNS server is slow or misconfigured — use a faster DNS server. ### Fix In POPcon PRO's antispam settings, remove any blacklist servers that are no longer responding, and reduce the DNS server list to a single, fast, working DNS server. Need more help? Contact support --- ## 451 4.7.0 Temporary server error PRX — Exchange 2013 fix Source: https://www.servolutions.com/support/articles/Temporaryservererror2013 Language: en ← Knowledge Base ### Exchange 2013 SMTP error "451 4.7.0 Temporary server error. Please try again later. PRX" This error has two common causes: ### A) Receive connector conflict If you have multiple receive connectors configured, there may be a conflict. Remove any duplicate or conflicting connectors and ensure the "Default Frontend [SERVERNAME]" connector is correctly configured with Anonymous Users permitted. ### B) TLS / DNS / network issues - Disable TLS on the receive connector (POPcon uses plain SMTP, not STARTTLS). - Disable any unused network adapters on the Exchange server. - Configure the server to use IPv4 only. - Verify DNS entries are correct and that the server clock is synchronized (use NTP). Need more help? Contact support --- ## There are .msg files in the POPcon folder with undistributed emails — how to redistribute them — Servolutions Support Source: https://www.servolutions.com/support/articles/undistributedmsgfiles Language: en ← Knowledge Base ### There are .msg files in the POPcon folder with undistributed emails — how to redistribute them POPcon stores downloaded emails as .msg files in its program folder while they are being delivered to Exchange. If Exchange was unavailable, these files remain there. ### To retry delivery - Move the .msg files from the main POPcon folder into the PICKUP subfolder (e.g. C:\Program Files (x86)\POPcon\PICKUP ). - POPcon will pick up files from the PICKUP folder during its next mail retrieval cycle and attempt delivery to Exchange again. Note: Do not move files while POPcon is actively processing. You may stop the service first if needed. Need more help? Contact support --- ## Why are emails to unknown recipients in my domain not forwarded to the postmaster? — Servolutions Support Source: https://www.servolutions.com/support/articles/unknownmailadr Language: en ← Knowledge Base ### Why are emails to unknown recipients in my domain not forwarded to the postmaster? POPcon v3.00 and later includes a built-in "Re-route email to unknown recipients" feature. When enabled, emails addressed to users who are not found in Exchange/Active Directory are redirected to the configured postmaster or administrator address. ### To enable In POPcon's POP3/IMAP account configuration, enable the option "Re-route email to unknown recipients to postmaster" and verify that a valid postmaster email address is set on the General configuration tab. Need more help? Contact support --- ## Emails to unknown Exchange recipients remain stuck in POPcon's queue — Servolutions Support Source: https://www.servolutions.com/support/articles/unknownrejected Language: en ← Knowledge Base ### Emails to unknown Exchange recipients remain stuck in POPcon's queue When Exchange rejects delivery for unknown recipients (users not in Active Directory), POPcon cannot forward the email and it stays in the queue. ### Option A: Disable recipient filtering in Exchange In Exchange System Manager, go to Global Settings > Message Delivery > Recipient Filtering and disable the filter. Exchange will then accept the message and generate an NDR internally. ### Option B: Configure POPcon to re-route unknown recipients In POPcon's POP3/IMAP configuration, enable "Re-route email to unknown recipients" and set a postmaster or catch-all address. Unknown recipients will be redirected there instead of getting stuck. ### Screenshots — step by step Exchange 2003 Server Global Settings Exchange 2003 Message Delivery Properties Need more help? Contact support --- ## 504 5.7.4 Unrecognized Authentication Type — Office 365 Source: https://www.servolutions.com/support/articles/Unrecognizedauthenticatio Language: en ← Knowledge Base ### "504 5.7.4 Unrecognized authentication type" when using Office 365 SMTP relay This error occurs when there is a mismatch between the TLS/SSL settings in MultiSendcon and what Office 365 requires. ### Fix In the MultiSendcon SMTP account settings for smtp.office365.com , change the SSL option to "Explicit SSL/TLS" . Note: Explicit SSL/TLS support was added in MultiSendcon version 2.10 . If you have an older version, download the current version first. Office 365 requires STARTTLS (explicit TLS on port 587). Plain SSL (implicit, port 465) is not supported for outbound relay through Office 365. Need more help? Contact support --- ## Microsoft 365 OAuth2 (Modern Auth) for POPcon — Setup Source: https://www.servolutions.com/support/articles/Usingoauthformicrosoft365 Language: en ← Knowledge Base ### Connect to Microsoft 365 or Outlook online accounts with OAuth2 Microsoft 365 and Outlook.com require OAuth2 (modern authentication). Configure as follows: - Set the server type to IMAP , server address outlook.office365.com , port 993 . - Set the authentication type to "OAuth2 Microsoft" . - Click "Connect OAuth2" . A Microsoft sign-in page opens in your browser. - Sign in and complete identity verification (MFA if required). - Grant POPcon permission to read your email. - Return to POPcon — the status should show "Authenticated" . - Click "Test access" to verify. No password entry is needed. The OAuth token is maintained and refreshed automatically by POPcon. Why Microsoft 365 refuses passwords, what the token does for an unattended service, and the symptoms behind a failing login are explained in the guide Basic authentication is gone: fetching a Microsoft 365 mailbox by IMAP or POP3 with OAuth2 into Exchange . ### Screenshots — step by step Note: The IP port number for Microsoft IMAP with OAuth is 993, as shown below. Click on the Connect OAuth2 button to start the OAuth authentication process. A web browser window will open, asking you to sign in with your Microsoft account. Microsoft will prompt you to verify your identity. You will receive a notification to your phone or other authentication methods to sign in securely. Verify your identity to proceed. Microsoft will ask for permission to allow POPcon email forwarding to read, update, create, and delete emails from your Outlook account. Review the permissions and click Accept to grant access. After authentication, the status in POPcon will show as Authenticated. You can now test the email account connection by clicking on the Test access button to ensure that everything is configured correctly. POPcon will test the connection to your Microsoft Office 365 or Outlook online account. If the test passes successfully, you are all set to retrieve emails using OAuth authentication. Need more help? Contact support --- ## Will I lose emails if Exchange is down when POPcon tries to deliver? — Servolutions Support Source: https://www.servolutions.com/support/articles/whatwhennoserver Language: en ← Knowledge Base ### Will I lose emails if Exchange is down when POPcon tries to deliver? No emails are lost. POPcon uses the SMTP protocol which requires explicit acknowledgment for every message delivered. Until Exchange confirms receipt, POPcon keeps the message in a temporary .msg file in its program folder. POPcon will retry delivery automatically on every subsequent mail retrieval cycle. Once Exchange is back online, all queued messages are delivered. Messages remain safe for as long as the POPcon server is running. No manual intervention is needed. Need more help? Contact support --- ## Why does POPcon need to know the "accepted domains" on the POP3/IMAP config tab? — Servolutions Support Source: https://www.servolutions.com/support/articles/whyaccepteddomains Language: en ← Knowledge Base ### Why does POPcon need to know the "accepted domains" on the POP3/IMAP config tab? When using a catch-all or multi-user POP3 mailbox, a single download may contain emails for many different recipients. POPcon must decide which recipients are local (to be delivered to Exchange) and which are not. Without a list of accepted domains, POPcon cannot filter correctly and may attempt to deliver to unknown addresses, causing Exchange errors or re-routing everything to the postmaster. Enter each domain you want POPcon to handle (e.g. yourcompany.com ) in the Accepted Recipient Domains field. This tells POPcon: "only deliver emails where the recipient address ends in one of these domains." Need more help? Contact support --- ## Configure Exchange 2000 for POPcon Source: https://www.servolutions.com/support/config-exchange-2000 Language: en ← Knowledge Base ### Configuration of Exchange 2000 Server [Please check out our related product Exchange POP3 connector POPcon . POPcon connects your MS Exchange Server to your POP3 mailboxes on the Internet. POPcon downloads emails from POP3 and IMAP mailboxes and distributes them to the appropriate Exchange Server users according to the recipient information found in the emails.] ### Exchange 2000 configuration Configuring your new Exchange 2000 server isn't hard if you just do it step by step as shown in this configuration sample. In this guide we will step through a sample installation of Exchange 2000 for a company we will call "Servolutions". Servolutions consequently owns the internet domain name "servolutions.com". Actually it only takes these five steps: - Adding your internet domain name to the recipient policies - Configuring the SMTP server for inbound email - Adding a SMTP Connector for outbound emails - Configuring the email addresses of your users - Installing and configuring POPcon or POPcon PRO And this is how to configure the Exchange Server to accept email for servolutions.com and work with POPcon: First install the software from CD. You may have to go back to the "Add/remove Software" utility in the control panel to add NNTP support if you did not do so during initial setup of your windows installation. ### 1. Adding your internet domain name to the recipient policies Open the Exchange System-Manager. It should look like this: One of the problems most often encountered when configuring an Exchange 2000 Server system is the fact that often the internet domain nane you want to receive email for ("yourcompany.com") does not match your standard active directory domain name (i.e. "servername.internetdomainname.com"). The Exchange 2000 Server component handling incoming emails - the SMTP server - does not accept emails for other domains than your standard active directory domain, even if you entered the correct email addresses ("user@yourinternetdomain.com") in the active directory. To make Exchange accept email for additional domains like your internet domain you need to add the domain names to the default recipient policy like this: On the main tree panel of the exchange system manager expand the tree "Recipients" and then click on "Recipient Policies". The policies will be shown on the right panel. Normally only the "Default Policy" will be there: Open the properties of the "Default Policy" by double-clicking it: In the Default Policy Properties please choose the tab "E-Mail Addresses". There you will find a list of domains supported by your exchange server. Usually only your internal active directory server domain will be listed here: Like you can see, after installing our Exchange Server from scratch only our AD domain "cs.christensen-software.com" was listed as accepted SMTP address. But emails from the internet will be comming in addressed to "@servolutions.com" and not cs.christensen-software.com! Choose "New..." here to add another accepted inbound domain. Since emails on the internet are sent via the SMTP protocol we want to add an "SMTP Address": Now enter the domain name you want to receive email for. Please add a leading "@" to the domain name. This is what we entered to support our new company "Servolutions": This is how the Default Policy Properties look like after entering the additional SMTP domain: When you OK the above dialog, Exchange will ask you with the next dialog box if you want to add the new address to all new users. Usually you do want exactly that to save some typing later. Please note: You may need to restart your server to activate the new domain! ### 2. Configuring the SMTP server for inbound email Next we will configure the SMTP-Server. This is the part of Exchange that accepts incoming emails from POPcon. No special settings are needed to work with POPcon but these are the standard settings in any case: You will find the settings for the SMTP server under Servers/Protocols/SMTP/Default SMTP Virtual Server: Open the properties by right-clicking on the Default SMTP Virtual Server and choosing "Properties": On the tab "Access" you can find some configuration settings that might interfere with POPcon. POPcon only works with a standard SMTP connection WITHOUT authentication, so allow "Anonymous access" in the "Authentication" dialog: Choose "Connection" to grant or refuse the right to connect to the SMTP server to individual or multiple IP Address Ranges. Please ensure the system POPcon runs on does have the right to connect granted. With this setting ALL system have access to your SMTP server: Under "Relay..." you can assign the right to relay through your SMTP-Server to some systems. This might be needed in some configuration and to be sure you should grant the system POPcon runs on relay rights. All other systems will need to authenticate before accessing the SMTP server to prevent unauthorized users using your system to relay spam: Under the "Messages" tab you can restrict message size and number of messages accepted for each connection. Please make sure these settings are liberal enough to allow POPcon to transmit large messages to your server. Also, on this tab you can choose an internal additional recipient for copies of the non-delivery reports. These NDRs will be sent back to senders of mails addressed to recipients unknown in your Exchange Server and they include a copy of the original message sent. You can use these postmaster copies of the NDRs to manually forward emails sent to mistyped recipients to the correct users. Under tab "Delivery" some more configuration settings for outgoing emails can be found: ### 3. Adding a SMTP Connector for outbound emails Now we need to add an SMTP- Connector (vs. SMTP Server ) to handle outgoing email to the Internet. Right-click "Connectors" in the Exchange System Manager and choose "New", "SMTP-Connector" to start adding the new connector: On the "General" tab you can now choose wether Exchange will send outgoing emails directly to the recipients system ("Use DNS...") or if all emails should be relayes through a SMTP relay server ("smart host"). The first option, DNS, is more direct but can sometimes cause problems when you use a dialup internet connection because some recipient systems will not accept emails that are coming from you ISP's dialup IP range while pretending to come from your real internet domain. Sending via your ISP's smart host / smtp relay server is the better option in this case. We chose "DNS" here, but if you do this as well and start receiving funny non-delivery reports you know why. Also, on the General tab you need to add the "local bridgehead" server: Exchange will already populate this dialog with the correct settings. This is the resulting General tab of the outbound SMTP-Connector after adding the local bridgehead: On the tab "Address Space" we need to add a wildcard address space for SMTP: We select "Add..." and then "SMTP": We want to allow emails to any domain, so we use the wildcard "*" here: Side note about the "Cost" entry: If you want to send emails to some domains via a different route you can create multiple SMTP connectors and set the "Cost" entry of this wildcard connector to a higher value while setting the cost entry of the special domain route to a lower cost but with only the special domain allowed on this page. This is especially useful if you generally want to send via DNS and only route to some systems that won't accept your email via some relay server. This is the resulting page: And that's alreay it - Your Exchange is now configured to send email to the internet and receive an SMTP email feed like it will come from POPcon or a direct internet connection. All you should do now is configure your users' email addresses in the Active directory. ### 4. Configuring your user's email addresses in the Active Directory You can set one or multiple email addresses for each user to receive email at. We will step through the neccessary actions when creating a new user called John Galt. First open the active directory and right-click the "Users" item to select "New", "User": The resulting dialog will allow you to create a new AD user to log into your server and creates an Exchange mailbox all in one wizard pass: Next... Next... Now the wizard continues into the Exchange Server realm and lets us create a new exchange mailbox We just accepted the default alias here. Next... Ok, fine - but wait: What about our desired email address? john@servolutions.com? We need to add this mail address manually. We are back at the AD configuration console and select the properties of our new user "John Galt" by right-clicking on the name: Lot's of tabs on this resulting dialog: We go to the "E-mail Addresses" tab: And surprise: john@servolutions.com is already there, but in suspiciously non-bold print. Actually, Exchange automatically entered this additional email address because we choose so during the editing of the default recipient policies. But we want this address to be the primary address meaning all email sent by John will get this address as the "senders" and "reply" addresses in the mail headers. So we click on "Set As Primary" and are done: We could also add more email addresses like info@servolutions.com or sales@servolutions.com but only one of these addresses can be the primary address that will be the default senders' address in all emails sent out by john. And that's really it - just step through your other user's AD entries and set the appropriate primary and additional email addresses. ### 5. Installing and configuring POPcon or POPcon PRO After going through the above 4 steps your Exchange is configured to send out email but it still can't pull down email from POP3 or IMAP mailboxes on your provider server. For this you need to install and configure POPcon. Configuring POPcon is quite straightforward. You need to follow these steps: a) Configure a Postmaster email address on the GENERAL configuration tab. b) Add one or more POP3 mailboxes on the POP3/IMAP tab. c) Configure the Exchange server name on the EXCHANGE configuration tab. Download and run the self-extracting installer of POPcon or POPcon PRO and follow the instructions during the installation. It will install the POPcon Administrator program and the POPcon service that runs in the background on your system. Run POPcon Adminstrator from Start > Programs > POPcon POPcon Screenshot Click on "Configure" to open up the POPcon configuration screen. ### a) Configure a Postmaster email address on the GENERAL configuration tab. On this first configuration page you only need to enter the email address of your Postmaster or Administrator user. The Postmaster will receive all emails without a valid recipient as well as general POPcon status notifications. It is very important to define a real email address from inside your exchange server here because mails can be lost irretrievably if POPcon forwards some mail with no recipient information to the postmaster and that account does not exist in your exchange server. You can leave the log file options to their default settings for now. Next go to the POP3/IMAP tab to configure the POP3 or IMAP mailbox accoutns you want POPcon to download email from. ### b) Add one or more POP3 mailboxes on the POP3/IMAP tab. POPcon PRO collects mail from as many POP3 accounts you like. Just click on Add to add another POP3 host or account to the list of Polled POP3 Hosts. For each server or account you need to fill in the POP3 server settings as shown below. If you are using catch-all style mailboxes (mailboxes that receive email for a whole domain, regardless of the recipient part before the "@") POPcon needs to filter recipients from incoming mail so only the recipients at your own internet domain are accepted. Please add the domain you consider your own in the "Accepted Recipient Domains" box. This is the same domain you configured earlier in the Exchange Default Policy. ### Individual account settings This dialog lets you input the specifics about a POP3 or an IMAP server you want to have polled by POPcon PRO. This is the information POPcon PRO needs to know about each server: ### Server type: Here you can select on the four supported server types: POP3: Default. POP3 servers are by far the most common mail server types on the internet. POP3-SSL: Some POP3 Servers need SSL encryption enabled for the connection in order to protect passwords and sensitive information. Choose this type to have a SSL-encrypted connection to a POP3 server. IMAP: IMAP Servers are also quite common and theoretically allow the client to manipulate email folders and move email between folders online. In our case the protocol is used to download email from the INBOX of the IMAP server to your exchange server. IMAP-SSL: Supports SSL connections to IMAP servers for added protection. ### Access: Configure the server name, account name and password to connect to the mail server here. Servername: The name the server you want to have polled. You can also enter the IP address directly. Username: The username needed to log into your POP3 or IMAP mail server. Password: The password needed to log into your mail server. IP portnumber: Almost always the TCP/IP port for POP3 mail is 110. Under some circumstances, internet routers or firewalls change the port number. Please ask your network administrator or internet provider. The standard port for POP3-SSL is 995, for IMAP it is 143 and for IMAP-SSL this should be set to 993. Timeout: Leave this to the default value. Please ask your POP3 mailbox hosting provider if you do not have the above information. ### Type of mailbox / distribution: POPcon PRO supports both catch-all and single user mailboxes Catch-all mailbox ("*@domainname.com"): For this type of mailbox, POPcon PRO will distribute the email retrieved from this server according to what it finds in the TO:, CC:, BCC: and other header-fields of the mail. If you choose this option, don’t forget to add your internet domain name(s) to the "Accepted Recipient Domains" box. on the POP3/IMAP configuration dialog Single user mailbox ("user@domainname.com"): This type of mailbox receives email for only one specific Exchange mailbox. You need to specify the receiver of the email here. POPcon PRO will then direct all mail retrieved from this server to the recipient email address given here. ### Delete / keep email on the server: This block allows you to configure POPcon PRO to either delete email after downloading or keep it on your POP3 or IMAP server for a specified amount of time or indefinitely. Delete downloaded email: This is the default setting – POPcon PRO will delete the Email on your POP3 or IMAP server after successfully downloading it. Leave a copy of downloaded email (indefinitely): This option will cause POPcon PRO to leave a copy of the email on the server. Only use this option during testing or when you are sure the mail will be deleted eventually, i.e. by another system periodically downloading an deleting email. Leave a copy of downloaded email for n number of days: Causes POPcon PRO to leave a copy of the email on the POP3/IMAP server for the specified number of days before deleting it. You can use this option to allow access to a single POP3 or IMAP mailbox by two different systems. ### c) Configure the Exchange server name on the EXCHANGE configuration tab. On this configuration screen you can specify the Exchange™-(SMTP) Server you want the mail to be directed to. Normally this will be the computer name of your Exchange™ server (like "MYSERVER"). You can leave all other settings default These three steps to configure POPcon will provide you with a working set-up. Test it out by confirming the new configuration with OK and then use the "Trigger mail retrieval" button on the POPcon Administrator main screen to start the first mail download. You can follow what is happening in the scrolling log display on that screen. Watch out for any error messages there. There is also a POPcon log file (c:\program files\POPcon\POPconSrv.log – open with notepad) that you can view at your leisure. --- ## Configure Exchange 2003 for POPcon — Step-by-Step Guide Source: https://www.servolutions.com/support/config-exchange-2003 Language: en ← Knowledge Base ### Configuration of Exchange 2003 Server Configuring your new Exchange 2003 server for internet email with POPcon for downloading the email from POP3 mailboxes isn't hard if you just do it step by step as shown in this configuration sample. In this guide we will step through a sample installation of Exchange 2003 for a company we will call "Mycompany". Mycompany consequently owns the internet domain name "mycompany.com". Actually it only takes these simple steps: - Adding your internet domain name to the recipient policies - Configuring the SMTP server for inbound email - Adding a SMTP Connector for outbound emails - Configuring the email addresses of your users - Installing and configuring POPcon, Exchange POP3 Connector This document is also available in German: Deutsch And this is how to configure the Exchange Server to accept email for a domain like "mycompany.com" and cooperate with POPcon: First install the Exchange server software from the CD or DVD. You may have to go back to the "Add/remove Software" utility in the control panel to add NNTP support if you did not do so during initial setup of your windows installation. Then open the Exchange System Manager and configure the new Exchange installation. ### 1. Adding your internet domain name to the recipient policies Open the Exchange System-Manager. It should look like this: One of the problems most often encountered when configuring an Exchange 2003 Server system is the fact that often the internet domain name you want to receive email for ("mycompany.com") does not match your standard active directory domain name (i.e. "servername.mycompany.com"). The Exchange 2003 Server component handling incoming emails - the SMTP server - does not accept emails for other domains than the ones entered in the "recipient policies", even if you entered the correct email addresses ("user@mycompany.com") in the active directory. To make Exchange accept email for additional domains like your internet domain you need to add the domain names to the default recipient policy like this: On the main tree panel of the Exchange system manager expand the tree "Recipients" and then click on "Recipient Policies". The policies will be shown on the right panel. Normally only the "Default Policy" will be there: Open the properties of the "Default Policy" by double-clicking it: In the Default Policy Properties please choose the tab "E-Mail Addresses". There you will find a list of domains supported by your exchange server. Usually only your internal active directory server domain will be listed here: Like you can see, after installing our Exchange Server from scratch only our AD domain "Christensen.local" was listed as accepted SMTP address. But emails from the internet will be coming in addressed to "@mycompany.com" and not Christensen.local! Choose "New..." here to add another accepted inbound domain. Since emails on the internet are sent via the SMTP protocol we want to add an "SMTP Address": Now enter the domain name you want to receive email for. Please add a leading "@" to the domain name. This is what we entered to support emails addressed to @mycompany.com: This is how the Default Policy Properties look like after entering the additional SMTP domain: Enable the newly created entry with a check mark next to it: When you OK the above dialog, Exchange will ask you with the next dialog box if you want to add the new address to all new users. Usually you do want exactly that to save some typing later. Please note: You may need to restart your server to activate the new domain! ### 2. Configuring the SMTP server for inbound email Next we will configure the SMTP-Server. This is the part of Exchange that accepts incoming emails from POPcon. No special settings are needed to work with POPcon but these are the standard settings in any case: You will find the settings for the SMTP server under Servers/Protocols/SMTP/Default SMTP Virtual Server. Open the properties by right-clicking on the Default SMTP Virtual Server and choosing "Properties": The settings on tab "General" can normally be left to the defaults. On the tab "Access" you can find some configuration settings that might interfere with POPcon. POPcon only works with a standard SMTP connection WITHOUT authentication, so allow "Anonymous access" in the "Authentication" dialog: Choose "Connection" to grant or refuse the right to connect to the SMTP server to individual or multiple IP Address Ranges. Please ensure the system that runs POPcon does have the right to connect granted. With this setting ALL systems will have access to your SMTP server: Under "Relay..." you can assign the right to relay through your SMTP-Server to some systems. This might be needed in some configuration and to be sure you should grant the system POPcon runs on relay rights. All other systems will need to authenticate before accessing the SMTP server to prevent unauthorized users using your system to relay spam: Under the "Messages" tab you can restrict message size and number of messages accepted for each connection. Please make sure these settings are liberal enough to allow POPcon to transmit large messages to your server. Also, on this tab you can choose an internal additional recipient for copies of the non-delivery reports. These NDRs will be sent back to senders of mails addressed to recipients unknown in your Exchange Server and they include a copy of the original message sent. You can use these postmaster copies of the NDRs to manually forward emails sent to mistyped recipients to the correct users. Under tab "Delivery" some more configuration settings for outgoing emails can be found: ### 3. Adding the SMTP Connector for outbound emails Now we need to add an SMTP-Connector (vs. SMTP Server) to handle outgoing email to the Internet. Right-click "Connectors" in the Exchange System Manager and choose "New", "SMTP-Connector" to start adding the new connector and name it appropriately (like "SMTP-Out" in our case): On the "General" tab you can now choose wether Exchange will send outgoing emails directly to the recipients system ("Use DNS...") or if all emails should be relayes through a SMTP relay server ("smart host"). The first option, DNS, is more direct but can sometimes cause problems when you use a dialup internet connection because some recipient systems will not accept emails that are coming from your ISP's dialup IP range while pretending to come from your real internet domain. Sending via your ISP's smart host / smtp relay server is the better option in this case. We choose our ISPs smtp relay server here. Also, on this tab you need to add the "local bridgehead" server (as shown above) On the tab "Address Space" we need to add a wildcard address space for SMTP. We want to allow emails to any domain, so we use the wildcard "*" here: Side note about the "Cost" entry: If you want to send emails to some domains via a different route you can create multiple SMTP connectors and set the "Cost" entry of this wildcard connector to a higher value while setting the cost entry of the special domain route to a lower cost but with only the special domain allowed on this page. This can be used if you generally want to send via DNS and only route to some systems that won't accept your email via some relay server. This allows your to instruct our Exchange server to use a different e-mail server (smart host) to send e-mails depending on the domain you send to . Unfortunately this is seldom useful and does not allow different smart hosts depending on the sender domain . If you want that please check out our MultiSendcon, the multi-domain send connector for Exchange If your ISP's SMTP server requires authentication (and almost all of them do today) you can set the username and password on the "Advanced" tab of the SMTP connector. Select "Outbound Security": Select "Basic authentication" and chose "Modify" to enter the username and password: And that's already it - Your Exchange is now configured to send email to the internet and receive an SMTP email feed like it will come from POPcon or a direct internet connection. All you should do now is configure your users' email addresses in the Active directory. ### 4. Configuring your users' email addresses in the Active Directory You can set one or multiple email addresses for each user to receive email at. We will step through the necessary actions when creating a new user called John Galt. First open the active directory and right-click the "Users" item to select "New", "User": The resulting dialog will allow you to create a new AD user to log into your server and creates an Exchange mailbox all in one wizard pass: Next... Next... Now the wizard continues into the Exchange Server realm and lets us create a new exchange mailbox We just accepted the default alias here. Next... Ok, fine - but wait: What about our desired email address? john@servolutions.com? We need to add this mail address manually. We are back at the AD configuration console and select the properties of our new user "John Galt" by right-clicking on the name: Lots of tabs on this resulting dialog: We go to the "E-mail Addresses" tab: And surprise: john@servolutions.com is already there, but in suspiciously non-bold print. Actually, Exchange automatically entered this additional email address because we chose so during the editing of the default recipient policies. But we want this address to be the primary address meaning all email sent by John will get this address as the "senders" and "reply" addresses in the mail headers. So we click on "Set As Primary" and are done: We could also add more email addresses like info@servolutions.com or sales@servolutions.com but only one of these addresses can be the primary address that will be the default senders' address in all emails sent out by John. And that's really it - just step through your other user's AD entries and set the appropriate primary and additional email addresses. ### 5. Installing and configuring POPcon or POPcon PRO After going through the above 4 steps your Exchange is configured to send out email but it still can't pull down email from POP3 or IMAP mailboxes on your provider server. For this you need to install and configure POPcon. Configuring POPcon is quite straightforward. You need to follow these steps: a) Configure a Postmaster email address on the GENERAL configuration tab. b) Add one or more POP3 mailboxes on the POP3/IMAP tab. c) Configure the Exchange server name on the EXCHANGE configuration tab. Download and run the self-extracting installer of POPcon or POPcon PRO and follow the instructions during the installation. It will install the POPcon Administrator program and the POPcon service that runs in the background on your system. Run POPcon Adminstrator from Start > Programs > POPcon POPcon Screenshot Click on "Configure" to open up the POPcon configuration screen. ### a) Configure a Postmaster email address on the GENERAL configuration tab. On this first configuration page you only need to enter the email address of your Postmaster or Administrator user. The Postmaster will receive all emails without a valid recipient as well as general POPcon status notifications. It is very important to define a real email address from inside your exchange server here because mails can be lost irretrievably if POPcon forwards some mail with no recipient information to the postmaster and that account does not exist in your exchange server. You can leave the log file options to their default settings for now. Next go to the POP3/IMAP tab to configure the POP3 or IMAP mailbox accounts you want POPcon to download email from. ### b) Add one or more POP3 mailboxes on the POP3/IMAP tab. POPcon PRO collects mail from as many POP3 accounts you like. Just click on Add to add another POP3 host or account to the list of Polled POP3 Hosts. For each server or account you need to fill in the POP3 server settings as shown below. If you are using catch-all style mailboxes (mailboxes that receive email for a whole domain, regardless of the recipient part before the "@") POPcon needs to filter recipients from incoming mail so only the recipients at your own internet domain are accepted. Please add the domain you consider your own in the "Accepted Recipient Domains" box. This is the same domain you configured earlier in the Exchange Default Policy. ### Individual accounts settings This dialog lets you input the specifics about a POP3 or an IMAP server you want to have polled by POPcon PRO. This is the information POPcon PRO needs to know about each server: ### Server type: Here you can select on the four supported server types: POP3: Default. POP3 servers are by far the most common mail server types on the internet. POP3-SSL: Some POP3 Servers need SSL encryption enabled for the connection in order to protect passwords and sensitive information. Choose this type to have a SSL-encrypted connection to a POP3 server. IMAP: IMAP Servers are also quite common and theoretically allow the client to manipulate email folders and move email between folders online. In our case the protocol is used to download email from the INBOX of the IMAP server to your exchange server. IMAP-SSL: Supports SSL connections to IMAP servers for added protection. ### Access: Configure the server name, account name and password to connect to the mail server here. Servername: The name the server you want to have polled. You can also enter the IP address directly. Username: The username needed to log into your POP3 or IMAP mail server. Password: The password needed to log into your mail server. IP portnumber: Almost always the TCP/IP port for POP3 mail is 110. Under some circumstances, internet routers or firewalls change the port number. Please ask your network administrator or internet provider. The standard port for POP3-SSL is 995, for IMAP it is 143 and for IMAP-SSL this should be set to 993. Timeout: Leave this to the default value. Please ask your POP3 mailbox hosting provider if you do not have the above information. ### Type of mailbox / distribution: POPcon PRO supports both catch-all and single user mailboxes Catch-all mailbox ("*@domainname.com"): For this type of mailbox, POPcon PRO will distribute the emails retrieved from this server according to what it finds in the TO:, CC:, BCC: and other header-fields of the mail. If you choose this option, don’t forget to add your internet domain name(s) to the "Accepted Recipient Domains" box on the POP3/IMAP configuration dialog Single user mailbox ("user@domainname.com"): This type of mailbox receives email for only one specific Exchange mailbox. You need to specify the receiver of the email here. POPcon PRO will then direct all mail retrieved from this server to the recipient email address given here. ### Delete / Keep email on the server: This block allows you to configure POPcon PRO to either delete email after downloading or keep it on your POP3 or IMAP server for a specified amount of time or indefinitely. Delete downloaded email: This is the default setting – POPcon PRO will delete the Email on your POP3 or IMAP server after successfully downloading it. Leave a copy of downloaded email (indefinitely): This option will cause POPcon PRO to leave a copy of the email on the server. Only use this option during testing or when you are sure the mail will be deleted eventually, i.e. by another system periodically downloading and deleting email. Leave a copy of downloaded email for n number of days: Causes POPcon PRO to leave a copy of the email on the POP3/IMAP server for the specified number of days before deleting it. You can use this option to allow access to a single POP3 or IMAP mailbox by two different systems. ### c) Configure the Exchange server name on the EXCHANGE configuration tab. On this configuration screen you can specify the Exchange™-(SMTP) Server you want the mail to be directed to. Normally this will be the computer name of your Exchange™ server (like "MYSERVER"). You can leave all other settings default These three steps to configure POPcon will provide you with a working set-up. Test it out by confirming the new configuration with OK and then use the "Trigger mail retrieval" button on the POPcon Administrator main screen to start the first mail download. You can follow what is happening in the scrolling log display on that screen. Watch out for any error messages there. There is also a POPcon log file (c:\program files\POPcon\POPconSrv.log – open with notepad) that you can view at your leisure. --- ## Configure Exchange 2007 for POPcon — Step-by-Step Guide Source: https://www.servolutions.com/support/config-exchange-2007 Language: en ← Knowledge Base ### Configuration of Exchange 2007 Server This guide shows the steps necessary to configure a newly installed Exchange 2007 server for receiving internet email via POPcon or POPcon PRO and for sending out emails to the internet. Basically you need to perform these simple steps: - Add your own internet domain to the “Accepted Domains” list - Configure a Send Connector for outgoing emails - Configure a Receive Connector for incoming emails (from POPcon) without Authentication - Assign email addresses to individual users in the active directory - Installing and configuring POPcon, Exchange POP3 Connector This document is also available in German: Deutsch ### 1. Add your own internet domain to the “Accepted Domains” list Open the Exchange Management Console and select Organisation Configuration, Hub Transport. In the middle pane select the Accepted Domains tab. There already will be one local domain configured here. You can leave it. Choose New Accepted Domain in the Actions pane. Choose a name for this domain (not important) and enter your internet domain name (in a domain.com format without @ or *@) as Accepted Domain. Also, select Authoritative Domain to tell Exchange to accept internet emails for this domain name and to tell Exchange that it is responsible for the whole domain. Remark: In the rare case where you want to only handle part of a domain in your Exchange, i.e. you only have a few email addresses of this domain in your Exchange and need Exchange to send out email to the internet for all other addresses inside this domain please select "External Relay Domain" instead to tell Exchange to accept internet emails for this domain name and to tell Exchange that it is responsible for only part of the domain. ### 2. Configure a send connector for outgoing emails The send connector is used to pipe outgoing emails from Exchange via your providers SMTP relay server to the internet. Select Organisation Configuration, Hub Transport in the Exchange Management Console. In the middle pane select the Send Connectors tab. And in the Actions pane click on New Send Connector We will add a new send connector. Choose any name (not important for the function) on the first page: On the next wizard page we need to specify an address space to be served for this connector. The address space „*“ means this send connector is sending out email to any domain on the internet. You can build additional specific send connectors for other target addresses, like “*@sistercompany.com” if there are special routing requirements. This allows your to instruct our Exchange server to use a different e-mail server (smart host) to send e-mails depending on the domain you send to . Unfortunately this is seldom useful and does not allow different smart hosts depending on the sender domain . If you want that please check out our MultiSendcon, the multi-domain send connector for Exchange On the next page we switch the configuration to Route email through your provider SMTP relay server (Smarthost in Exchange terms) and add the provider server address. The other option (use DNS without a relay server) can only be used when you are connected on a fixed IP address and host the webpages yourself. The last page of the wizard is needed to enter the provider SMTP relay servers username/password credentials. Almost all provider servers require you to log in before you can use their relay servers to send out email to protect against spam senders. It does not matter which users login data you use, this will not change the email content. Any provider SMTP server login will do. ### 3. Configure the receive connector for incoming email POPcon uses SMTP to forward emails to Exchange. For this to work we need to change two Exchange 2007 default configuration settings: The maximum email size is fixed to 10MB here and we need to add the anonymous user to the permission group in order to allow POPcon to transfer email. Important: You also need to make sure to not install the Windows "Simple Mail Transfer Protocol" service. This service could block the Exchange SMTP transport from actually answering the SMTP IP port (25) and could cause Emails to loop back to the internet if installed. Check Administrative tools, Services and disable this service. We can find these configuration settings under Server Configuration, Hub Transport, Receive Connectors, Properties of the Default Receive Connector: The maximum message size is fixed to 10240KB (10MB) by default on the General tab of these properties. Change that to 102400 (100MB) in order not to allow longer emails to come through. You can always limit individual user’s allowed maximum email sizes. We also need to add the Anonymous users to the Permission Groups tab in order to allow POPcon to connect to this receive connector at all. ### 4. Assign email addresses to users in the active directory All you need to do now is to add SMTP email addresses to users in the active directory. Users can have more than one SMTP address, for example they can have info@yourcompany.com in addition to jeff.smith@yourcompany.com. Exchange provides the convenient E-Mail Address Policies feature that allows you to assign identically formatted email addresses to all (including future) users. Open up Organization Configuration, Hub Transport, E-Mail Address Policies and click on New E-mail Address Policy in the actions pane. You can assign a (non-essential) name to the new policy: And then add a new E-Mail Addresses format on the next page: Enter your domain name and select one of the formats: ### 5. Installing and configuring POPcon or POPcon PRO After going through the above 4 steps your Exchange is configured to send out email but it still can't pull down email from POP3 or IMAP mailboxes on your provider server. For this you need to install and configure POPcon. Configuring POPcon is quite straightforward. You need to follow these steps: a) Configure a Postmaster email address on the GENERAL configuration tab. b) Add one or more POP3 mailboxes on the POP3/IMAP tab. c) Configure the Exchange server name on the EXCHANGE configuration tab. Download and run the self-extracting installer of POPcon or POPcon PRO and follow the instructions during the installation. It will install the POPcon Administrator program and the POPcon service that runs in the background on your system. Run POPcon Adminstrator from Start > Programs > POPcon POPcon Screenshot Click on "Configure" to open up the POPcon configuration screen. ### a) Configure a Postmaster email address on the GENERAL configuration tab. On this first configuration page you only need to enter the email address of your Postmaster or Administrator user. The Postmaster will receive all emails without a valid recipient as well as general POPcon status notifications. It is very important to define a real email address from inside your exchange server here because mails can be lost irretrievably if POPcon forwards some mail with no recipient information to the postmaster and that account does not exist in your exchange server. You can leave the log file options to their default settings for now. Next go to the POP3/IMAP tab to configure the POP3 or IMAP mailbox accoutns you want POPcon to download email from. ### b) Add one or more POP3 mailboxes on the POP3/IMAP tab. POPcon PRO collects mail from as many POP3 accounts you like. Just click on Add to add another POP3 host or account to the list of Polled POP3 Hosts. For each server or account you need to fill in the POP3 server settings as shown below. If you are using catch-all style mailboxes (mailboxes that receive email for a whole domain, regardless of the recipient part before the "@") POPcon needs to filter recipients from incoming mail so only the recipients at your own internet domain are accepted. Please add the domain you consider your own in the "Accepted Recipient Domains" box. This is the same domain you configured earlier in the Exchange Default Policy. ### Individual account settings This dialog lets you input the specifics about a POP3 or an IMAP server you want to have polled by POPcon PRO. This is the information POPcon PRO needs to know about each server: ### Server type: Here you can select on the four supported server types: POP3: Default. POP3 servers are by far the most common mail server types on the internet. POP3-SSL: Some POP3 Servers need SSL encryption enabled for the connection in order to protect passwords and sensitive information. Choose this type to have a SSL-encrypted connection to a POP3 server. IMAP: IMAP Servers are also quite common and theoretically allow the client to manipulate email folders and move email between folders online. In our case the protocol is used to download email from the INBOX of the IMAP server to your exchange server. IMAP-SSL: Supports SSL connections to IMAP servers for added protection. ### Access: Configure the server name, account name and password to connect to the mail server here. Servername: The name the server you want to have polled. You can also enter the IP address directly. Username: The username needed to log into your POP3 or IMAP mail server. Password: The password needed to log into your mail server. IP portnumber: Almost always the TCP/IP port for POP3 mail is 110. Under some circumstances, internet routers or firewalls change the port number. Please ask your network administrator or internet provider. The standard port for POP3-SSL is 995, for IMAP it is 143 and for IMAP-SSL this should be set to 993. Timeout: Leave this to the default value. Please ask your POP3 mailbox hosting provider if you do not have the above information. ### Type of mailbox / distribution: POPcon PRO supports both catch-all and single user mailboxes Catch-all mailbox ("*@domainname.com"): For this type of mailbox, POPcon PRO will distribute the email retrieved from this server according to what it finds in the TO:, CC:, BCC: and other header-fields of the mail. If you choose this option, don’t forget to add your internet domain name(s) to the "Accepted Recipient Domains" box. on the POP3/IMAP configuration dialog Single user mailbox ("user@domainname.com"): This type of mailbox receives email for only one specific Exchange mailbox. You need to specify the receiver of the email here. POPcon PRO will then direct all mail retrieved from this server to the recipient email address given here. ### Delete / keep email on the server: This block allows you to configure POPcon PRO to either delete email after downloading or keep it on your POP3 or IMAP server for a specified amount of time or indefinitely. Delete downloaded email: This is the default setting – POPcon PRO will delete the Email on your POP3 or IMAP server after successfully downloading it. Leave a copy of downloaded email (indefinitely): This option will cause POPcon PRO to leave a copy of the email on the server. Only use this option during testing or when you are sure the mail will be deleted eventually, i.e. by another system periodically downloading an deleting email. Leave a copy of downloaded email for n number of days: Causes POPcon PRO to leave a copy of the email on the POP3/IMAP server for the specified number of days before deleting it. You can use this option to allow access to a single POP3 or IMAP mailbox by two different systems. ### c) Configure the Exchange server name on the EXCHANGE configuration tab. On this configuration screen you can specify the Exchange™-(SMTP) Server you want the mail to be directed to. Normally this will be the computer name of your Exchange™ server (like "MYSERVER"). You can leave all other settings default These three steps to configure POPcon will provide you with a working set-up. Test it out by confirming the new configuration with OK and then use the "Trigger mail retrieval" button on the POPcon Administrator main screen to start the first mail download. You can follow what is happening in the scrolling log display on that screen. Watch out for any error messages there. There is also a POPcon log file (c:\program files\POPcon\POPconSrv.log – open with notepad) that you can view at your leisure. --- ## Configure Exchange 2010 for POPcon — Step by Step Source: https://www.servolutions.com/support/config-exchange-2010 Language: en ← Knowledge Base ### Configuration of Exchange 2010 Server This guide shows the steps necessary to configure a newly installed Exchange 2010 server for receiving email from POPcon or POPcon PRO and for sending out emails to the internet. Basically you need to perform these simple steps: - Add your own internet domain to the “Accepted Domains” list - Configure a Send Connector for outgoing emails - Configure a Receive Connector for incoming emails (from POPcon) without Authentication - Assign email addresses to individual users in the active directory - Installing and configuring POPcon, Exchange POP3 Connector This document is also available in German: Deutsch ### 1. Add your own internet domain to the “Accepted Domains” list Open the Exchange Management Console and select Organization Configuration, Hub Transport. In the middle pane select the Accepted Domains tab. There already will be one local domain configured here. You can leave it. Choose New Accepted Domain in the Actions pane. Choose a name for this domain (not important) and enter your internet domain name (in a domain.com format without @ or *@) as Accepted Domain. Also, select Authoritative Domain to tell Exchange to accept internet emails for this domain name and to tell Exchange that it is responsible for the whole domain. Remark: In the rare case where you want to only handle part of a domain in your Exchange, i.e. you only have a few email addresses of this domain in your Exchange and need Exchange to send out email to the internet for all other addresses inside this domain please select "External Relay Domain" instead to tell Exchange to accept internet emails for this domain name and to tell Exchange that it is responsible for only part of the domain. ### 2. Configure a send connector for outgoing emails The send connector is used to pipe outgoing emails from Exchange via your providers SMTP relay server to the internet. Select Organisation Configuration, Hub Transport in the Exchange Management Console. In the middle pane select the Send Connectors tab. And in the Actions pane click on New Send Connector We will add a new send connector. Choose any name (not important for the function) on the first page: On the next wizard page we need to specify an address space to be served for this connector. The address space „*“ means this send connector is sending out email to any domain on the internet. You can build additional specific send connectors for other target addresses, like “*@sistercompany.com” if there are special routing requirements. This allows your to instruct our Exchange server to use a different e-mail server (smart host) to send e-mails depending on the domain you send to . Unfortunately this is seldom useful and does not allow different smart hosts depending on the sender domain . If you want that please check out our MultiSendcon, the multi-domain send connector for Exchange On the next page we switch the configuration to Route email through your provider SMTP relay server (Smarthost in Exchange terms) and add the provider server address. The other option (use DNS without a relay server) can only be used when you are connected on a fixed IP address and host the webpages yourself. The last page of the wizard is needed to enter the provider SMTP relay servers username/password credentials. Almost all provider servers require you to log in before you can use their relay servers to send out email to protect against spam senders. It does not matter which users login data you use, this will not change the email content. Any provider SMTP server login will do. ### 3. Configure the receive connector for incoming email POPcon uses SMTP to forward emails to Exchange. For this to work we need to change two Exchange 2010 default configuration settings: The maximum email size is fixed to 10MB here and we need to add the anonymous user to the permission group in order to allow POPcon to transfer email. Important: You also need to make sure to not install the Windows "Simple Mail Transfer Protocol" service. This service could block the Exchange SMTP transport from actually answering the SMTP IP port (25) and could cause Emails to loop back to the internet if installed. Check Administrative tools, Services and disable this service. We can find these configuration settings under Server Configuration, Hub Transport, Receive Connectors, Properties of the Default Receive Connector: The maximum message size is fixed to 10240KB (10MB) by default on the General tab of these properties. Change that to 102400 (100MB) in order not to allow longer emails to come through. You can always limit individual user’s allowed maximum email sizes. We also need to add the Anonymous users to the Permission Groups tab in order to allow POPcon to connect to this receive connector at all. ### 4. Assign email addresses to users in the active directory All you need to do now is to add SMTP email addresses to users in the active directory. Users can have more than one SMTP address, for example they can have info@yourcompany.com in addition to jeff.smith@yourcompany.com. Exchange provides the convenient E-Mail Address Policies feature that allows you to assign identically formatted email addresses to all (including future) users. Open up Organization Configuration, Hub Transport, E-Mail Address Policies and click on New E-mail Address Policy in the actions pane. You can assign a (non-essential) name to the new policy: And then add a new E-Mail Addresses format on the next page: Enter your domain name and select one of the formats: ### 5. Installing and configuring POPcon or POPcon PRO After going through the above 4 steps your Exchange is configured to send out email but it still can't pull down email from POP3 or IMAP mailboxes on your provider server. For this you need to install and configure POPcon. Configuring POPcon is quite straightforward. You need to follow these steps: a) Configure a Postmaster email address on the GENERAL configuration tab. b) Add one or more POP3 mailboxes on the POP3/IMAP tab. c) Configure the Exchange server name on the EXCHANGE configuration tab. Download and run the self-extracting installer of POPcon or POPcon PRO and follow the instructions during the installation. It will install the POPcon Administrator program and the POPcon service that runs in the background on your system. Run POPcon Adminstrator from Start > Programs > POPcon POPcon Screenshot Click on "Configure" to open up the POPcon configuration screen. ### a) Configure a Postmaster email address on the GENERAL configuration tab. On this first configuration page you only need to enter the email address of your Postmaster or Administrator user. The Postmaster will receive all emails without a valid recipient as well as general POPcon status notifications. It is very important to define a real email address from inside your exchange server here because mails can be lost irretrievably if POPcon forwards some mail with no recipient information to the postmaster and that account does not exist in your exchange server. You can leave the log file options to their default settings for now. Next go to the POP3/IMAP tab to configure the POP3 or IMAP mailbox accoutns you want POPcon to download email from. ### b) Add one or more POP3 mailboxes on the POP3/IMAP tab. POPcon PRO collects mail from as many POP3 accounts you like. Just click on Add to add another POP3 host or account to the list of Polled POP3 Hosts. For each server or account you need to fill in the POP3 server settings as shown below. If you are using catch-all style mailboxes (mailboxes that receive email for a whole domain, regardless of the recipient part before the "@") POPcon needs to filter recipients from incoming mail so only the recipients at your own internet domain are accepted. Please add the domain you consider your own in the "Accepted Recipient Domains" box. This is the same domain you configured earlier in the Exchange Default Policy. ### Individual account settings This dialog lets you input the specifics about a POP3 or an IMAP server you want to have polled by POPcon PRO. This is the information POPcon PRO needs to know about each server: ### Server type: Here you can select on the four supported server types: POP3: Default. POP3 servers are by far the most common mail server types on the internet. POP3-SSL: Some POP3 Servers need SSL encryption enabled for the connection in order to protect passwords and sensitive information. Choose this type to have a SSL-encrypted connection to a POP3 server. IMAP: IMAP Servers are also quite common and theoretically allow the client to manipulate email folders and move email between folders online. In our case the protocol is used to download email from the INBOX of the IMAP server to your exchange server. IMAP-SSL: Supports SSL connections to IMAP servers for added protection. ### Access: Configure the server name, account name and password to connect to the mail server here. Servername: The name the server you want to have polled. You can also enter the IP address directly. Username: The username needed to log into your POP3 or IMAP mail server. Password: The password needed to log into your mail server. IP portnumber: Almost always the TCP/IP port for POP3 mail is 110. Under some circumstances, internet routers or firewalls change the port number. Please ask your network administrator or internet provider. The standard port for POP3-SSL is 995, for IMAP it is 143 and for IMAP-SSL this should be set to 993. Timeout: Leave this to the default value. Please ask your POP3 mailbox hosting provider if you do not have the above information. ### Type of mailbox / distribution: POPcon PRO supports both catch-all and single user mailboxes Catch-all mailbox ("*@domainname.com"): For this type of mailbox, POPcon PRO will distribute the email retrieved from this server according to what it finds in the TO:, CC:, BCC: and other header-fields of the mail. If you choose this option, don’t forget to add your internet domain name(s) to the "Accepted Recipient Domains" box. on the POP3/IMAP configuration dialog Single user mailbox ("user@domainname.com"): This type of mailbox receives email for only one specific Exchange mailbox. You need to specify the receiver of the email here. POPcon PRO will then direct all mail retrieved from this server to the recipient email address given here. ### Delete / keep email on the server: This block allows you to configure POPcon PRO to either delete email after downloading or keep it on your POP3 or IMAP server for a specified amount of time or indefinitely. Delete downloaded email: This is the default setting – POPcon PRO will delete the Email on your POP3 or IMAP server after successfully downloading it. Leave a copy of downloaded email (indefinitely): This option will cause POPcon PRO to leave a copy of the email on the server. Only use this option during testing or when you are sure the mail will be deleted eventually, i.e. by another system periodically downloading an deleting email. Leave a copy of downloaded email for n number of days: Causes POPcon PRO to leave a copy of the email on the POP3/IMAP server for the specified number of days before deleting it. You can use this option to allow access to a single POP3 or IMAP mailbox by two different systems. ### c) Configure the Exchange server name on the EXCHANGE configuration tab. On this configuration screen you can specify the Exchange™-(SMTP) Server you want the mail to be directed to. Normally this will be the computer name of your Exchange™ server (like "MYSERVER"). You can leave all other settings default These three steps to configure POPcon will provide you with a working set-up. Test it out by confirming the new configuration with OK and then use the "Trigger mail retrieval" button on the POPcon Administrator main screen to start the first mail download. You can follow what is happening in the scrolling log display on that screen. Watch out for any error messages there. There is also a POPcon log file (c:\program files\POPcon\POPconSrv.log – open with notepad) that you can view at your leisure. Coming from Windows SBS 2011, whose console had its own POP3 Connector? The guide The SBS 2008/2011 POP3 Connector: what it did, its limits, and the replacement compares it feature by feature with POPcon and lists the migration steps. --- ## Configure Exchange 2013 / 2016 for POPcon — Setup Guide Source: https://www.servolutions.com/support/config-exchange-2013 Language: en ← Knowledge Base ### Configuration of Exchange 2013 or 2016 Server This guide shows the steps necessary to configure a newly installed Exchange 2013 or 2016 server for receiving email from POPcon or POPcon PRO (or from the internet directly) and for sending out emails to the internet. Basically you need to perform these simple steps: - Add your own internet domain to the “Accepted Domains” list - Configure a Send Connector for outgoing emails - Configure the Default Frontend Receive Connector for incoming emails (from POPcon) without Authentication - Assign email addresses to users - Install and configure POPcon to download POP3 emails ### 1. Add your own internet domain to the “Accepted Domains” list In contrast with previous versions of Exchange (2010, 2007, 2003), there is no longer the MMC application to manage the server. Everything is done with the new Exchange Control Panel (ECP) and the Exchange Management Shell (EMS). Open the Internet browser and go to the following address: https://exchange. your-domain /ecp It will redirect us to the login screen in order to authenticate before accessing the ECP. Once you have entered your credentials, the ECP window appears: As we've already mentioned, all of the management operations happen here. The first step to configure our server is to add our Internet domain to the "Accepted Domains" list. To do so, go to the Mail Flow option (on the left pane) and select “Accepted Domains” in the menu bar above. There should be a default setting, usually the internal domain name (here servolutions.dom) that you can leave as it is. Now, add a new accepted domain by clicking on the "+" icon: Now, a pop-up window opens. Add the Internet domain that we want our server to accept. In the "Name" field enter a descriptive name for our rule (In this case, "Domain name for the Internet" is the name that I've chosen). In the Accepted domain field enter the name of your Internet domain name (in this case, servolutions.com). Mark the "Authoritative domain" option and once done, click the SAVE button in the lower part of the window. This setting indicates that this Exchange server will accept e-mails directed to the "servolutions.com" domain. The Authoritative domain option is to indicate that this server will be the one that processes all of the e-mails sent to the servolutions.com domain. ### 2. Configure a send connector for outgoing emails The send connector is used to pipe outgoing emails from Exchange via your providers SMTP relay server to the internet. In Exchange 2013 the “Hub Transport” role that existed in Exchange 2010 and 2007, is now integrated to the Mailbox server role. So now, all you have to do is click on the Send Connectors menu option. Here, we add a new send connector by clicking on the "+" icon. A new window will open. In the "Name" field enter a descriptive name for the connector (I've named it "Send Internet Mail"), select the Internet option and click in next . In most cases your Exchange server will be on a normal internet connection with a dynamic IP address and you should use the webspace provider's SMTP relay server to send out internet through. This ensures our emails are not flagged as spam by the receiving end since it originate from a public IP address. So in Exchange terms we will use a relay “Smart host” to send e-mail. For this option please select "Route mail through smart hosts" and in the next field add the smart host's address (FQDN). Once finished, click on Save. The configuration will look like the image shown below. Click Next . In the next window we will enter the authentication data for the SMTP relay server / smart host. Every commercial relay server requires authentication to keep spammers from abusing them. Choose "Basic authentication" and enter your provider's SMTP server username and password. Note that if you have multiple logins for the server it is not important which one you use. It will not affect the email sender name, this log in is purely used to allow you to send email through the relay server. Click on the Next button. The next screen asks for the send connector e-mail routing rules. Here we can instruct our Exchange server to use a different e-mail server (smart host) to send e-mails depending on the domain we send to . This is seldom useful and does not allow different smart hosts depending on the sender domain . If you want that please check out our MultiSendcon, the multi-domain send connector for Exchange In our case only one server is required, so in the next screen we should put an asterisk "*" in the "Domain" field. The asterisk means that e-mail to any other domain outside our organization will be routed through this external smart host. Click on the Next button. Another window will appear. In this screen we can indicate in which Exchange server this rule will apply. In this case, it applies to our one Exchange server. To set this rule, click on the “+” button and the next window (below) will appear. Here we select the server that this rule will apply. As we have one Exchange server only, we select it here and then click on the "add->" button, so it should look like this: Once finished just click on the OK button and it'll return to the previous window with the changes made. Once we are satisfied with the changes, click on finish . And now we're finished with our outgoing e-mail rule. But one more change should be applied to make it complete: The maximum outgoing message size is set to 10MB by default. This is how to change it: Please click the pencil icon to review and edit our changes: Change the maximum message size for outgoing emails to a value that is more convenient here and save the changes clicking on the Save button. With this done, we’re finished with the outgoing mail configuration. Now we’re ready to take a look at the e-mail receiving configuration. ### 3. Configure the "Default Frontend" receive connector for incoming email POPcon uses SMTP to forward emails to Exchange. For this to work we need to have a Receive Connector configured on the Exchange 2013 side and make sure the configuration settings of the new receive connector are correct, especially the maximum email size (which is set to 10MB by default and can cause many problems) and we need to add the anonymous user to the permission group in order to allow POPcon to transfer email into the Exchange server. Important: You also need to make sure to not install the Windows "Simple Mail Transfer Protocol" service. This service could block the Exchange SMTP transport from actually answering the SMTP IP port (25) and could cause Emails to loop back to the internet if installed. Check Administrative tools, Services and disable this service in case it is installed. Back to the Exchange configuration: In order to configure the incoming mail rules, open the Exchange Control Panel, go to the "Mail Flow" option located on the left pane and in the right pane, click on "Receive Connectors". The screen will look like the one pictured below. Select the "Default Frontend" connector and click the pencil icon to change the settings. In the General option we need to change the "“Maximum receive message size" from the default 10MB to 100MB, so larger E-Mails don't get stuck between POPcon and the Exchange Server. If you want you can later limit the maximum message size in the Exchange general options or even for an individual user in their mailbox options and cause Exchange to return undeliverable messages if the email is too large. Check the image below: Once finished, click on the save button. Now go to the Security option. Make sure to mark the checkbox which says "Anonymous users" (inside the red square in the image below). Anonymous users are all email senders from outside your organiation, so this check mark allows email senders from outside to deliver email into Exchange. Check the "Anonymous users" checkbox and click on the save button. Now, go to the Scoping option. Make sure to the Exchange server's real IP address, like in the image below. Also make sure that the "Network adapter bindings" option shows the server's IP address or "All available IPv4" and port 25. You can change the FQDN field to reflect the mail server’s fully qualified hostname or you can leave it as it is. That option is not important for POPcon. Click on the save button. With that, we're finished setting up our receive connector. ### 4. Assign email addresses to users All you need to do now is to add SMTP email addresses to users in the active directory. Users can have more than one SMTP address, for example they can have info@yourcompany.com in addition to jeff.smith@yourcompany.com. Exchange provides the convenient E-Mail Address Policies feature that allows you to assign identically formatted email addresses to all (including future) users. We edit the default email address policy like this: Open the Exchange Control Panel and select the Mail Flow option on the left pane, then select Email Address Policies menu option on the right pane. Select the default policy and click on the edit/pencil icon. This opens the E-mail address format window. Go straight to "Email Adress Format" and click in the edit button (again, the pencil icon). Select the domain in which we want to apply the new rule (in this example, servolutions.com) and below we can select the format that we will use for all of our e-mail addresses (in this case John.Smith@servolutions.com ). Finally, we mark the checkbox named "Make this format the reply email address" in order to force users to use this naming rule. Once finished, click on Save . Once the changes are saved, the Default Policy window will be updated. And that's really all. Now the server is correctly set up to send email out to the internet, receive internet from the internet (via POPcon - see below) and we have given users appropriate email addresses. ### 5. Installing and configuring POPcon or POPcon PRO After going through the above 4 steps your Exchange is configured to send out email but it still can't pull down email from POP3 or IMAP mailboxes on your provider server. For this you need to install and configure POPcon. Configuring POPcon is quite straightforward. You need to follow these steps: a) Configure a Postmaster email address on the GENERAL configuration tab. b) Add one or more POP3 mailboxes on the POP3/IMAP tab. c) Configure the Exchange server name on the EXCHANGE configuration tab. Download and run the self-extracting installer of POPcon or POPcon PRO and follow the instructions during the installation. It will install the POPcon Administrator program and the POPcon service that runs in the background on your system. Run POPcon Adminstrator from Start > Programs > POPcon POPcon Screenshot Click on "Configure" to open up the POPcon configuration screen. ### a) Configure a Postmaster email address on the GENERAL configuration tab. On this first configuration page you only need to enter the email address of your Postmaster or Administrator user. The Postmaster will receive all emails without a valid recipient as well as general POPcon status notifications. It is very important to define a real email address from inside your exchange server here because mails can be lost irretrievably if POPcon forwards some mail with no recipient information to the postmaster and that account does not exist in your exchange server. You can leave the log file options to their default settings for now. Next go to the POP3/IMAP tab to configure the POP3 or IMAP mailbox accoutns you want POPcon to download email from. ### b) Add one or more POP3 mailboxes on the POP3/IMAP tab. POPcon PRO collects mail from as many POP3 accounts you like. Just click on Add to add another POP3 host or account to the list of Polled POP3 Hosts. For each server or account you need to fill in the POP3 server settings as shown below. If you are using catch-all style mailboxes (mailboxes that receive email for a whole domain, regardless of the recipient part before the "@") POPcon needs to filter recipients from incoming mail so only the recipients at your own internet domain are accepted. Please add the domain you consider your own in the "Accepted Recipient Domains" box. This is the same domain you configured earlier in the Exchange Default Policy. ### Individual account settings This dialog lets you input the specifics about a POP3 or an IMAP server you want to have polled by POPcon PRO. This is the information POPcon PRO needs to know about each server: ### Server type: Here you can select on the four supported server types: POP3: Default. POP3 servers are by far the most common mail server types on the internet. POP3-SSL: Some POP3 Servers need SSL encryption enabled for the connection in order to protect passwords and sensitive information. Choose this type to have a SSL-encrypted connection to a POP3 server. IMAP: IMAP Servers are also quite common and theoretically allow the client to manipulate email folders and move email between folders online. In our case the protocol is used to download email from the INBOX of the IMAP server to your exchange server. IMAP-SSL: Supports SSL connections to IMAP servers for added protection. ### Access: Configure the server name, account name and password to connect to the mail server here. Servername: The name the server you want to have polled. You can also enter the IP address directly. Username: The username needed to log into your POP3 or IMAP mail server. Password: The password needed to log into your mail server. IP portnumber: Almost always the TCP/IP port for POP3 mail is 110. Under some circumstances, internet routers or firewalls change the port number. Please ask your network administrator or internet provider. The standard port for POP3-SSL is 995, for IMAP it is 143 and for IMAP-SSL this should be set to 993. Timeout: Leave this to the default value. Please ask your POP3 mailbox hosting provider if you do not have the above information. ### Type of mailbox / distribution: POPcon PRO supports both catch-all and single user mailboxes Catch-all mailbox ("*@domainname.com"): For this type of mailbox, POPcon PRO will distribute the email retrieved from this server according to what it finds in the TO:, CC:, BCC: and other header-fields of the mail. If you choose this option, don’t forget to add your internet domain name(s) to the "Accepted Recipient Domains" box. on the POP3/IMAP configuration dialog Single user mailbox ("user@domainname.com"): This type of mailbox receives email for only one specific Exchange mailbox. You need to specify the receiver of the email here. POPcon PRO will then direct all mail retrieved from this server to the recipient email address given here. ### Delete / keep email on the server: This block allows you to configure POPcon PRO to either delete email after downloading or keep it on your POP3 or IMAP server for a specified amount of time or indefinitely. Delete downloaded email: This is the default setting – POPcon PRO will delete the Email on your POP3 or IMAP server after successfully downloading it. Leave a copy of downloaded email (indefinitely): This option will cause POPcon PRO to leave a copy of the email on the server. Only use this option during testing or when you are sure the mail will be deleted eventually, i.e. by another system periodically downloading an deleting email. Leave a copy of downloaded email for n number of days: Causes POPcon PRO to leave a copy of the email on the POP3/IMAP server for the specified number of days before deleting it. You can use this option to allow access to a single POP3 or IMAP mailbox by two different systems. ### c) Configure the Exchange server name on the EXCHANGE configuration tab. On this configuration screen you can specify the Exchange™-(SMTP) Server you want the mail to be directed to. Normally this will be the computer name of your Exchange™ server (like "MYSERVER"). You can leave all other settings default These three steps to configure POPcon will provide you with a working set-up. Test it out by confirming the new configuration with OK and then use the "Trigger mail retrieval" button on the POPcon Administrator main screen to start the first mail download. You can follow what is happening in the scrolling log display on that screen. Watch out for any error messages there. There is also a POPcon log file (c:\program files\POPcon\POPconSrv.log – open with notepad) that you can view at your leisure. --- ## Configure Exchange 5.5 for POPcon Source: https://www.servolutions.com/support/config-exchange-55 Language: en ← Knowledge Base ### Configuration of Exchange Server 5.5 A brief setup guide for Exchange 5.5. Note: POPcon does not use SMTP authentication — Exchange 5.5 must be configured to accept anonymous SMTP connections. ### 1. Install the Internet Mail Service (IMS) The IMS component handles SMTP for Exchange 5.5. It may not be installed by default — install it from the Exchange 5.5 installation CD if needed. ### 2. Add the IMS in Exchange Administrator Open Exchange Server Administrator and add the Internet Mail Service under the Connections section. ### 3. Configure IMS Settings - Routing tab: Add your internet domain and set it to route to “” to receive SMTP email for your domain. - Connections tab: Select Inbound and outbound . For outbound, configure DNS routing or an ISP SMTP relay server. - Address-Space tab: Add SMTP address space * . Allow unauthenticated SMTP from all hosts (or restrict to the POPcon host IP only). - Delivery Restrictions tab: Accept email from all sources; restrict to nobody for sending. - Internet Mail tab: Set the postmaster/administrator account. ### 4. Install and Configure POPcon - Download and install POPcon from the download page . - General tab: Enter a postmaster email address. - POP3/IMAP tab: Add mailbox accounts (server, username, password, port). Ports: POP3 110, POP3-SSL 995, IMAP 143, IMAP-SSL 993. - Exchange tab: Enter the Exchange server name. - Click Trigger mail retrieval to test. --- ## POPcon Knowledge Base & Exchange Error Fixes — Servolutions Source: https://www.servolutions.com/support/knowledgebase Language: en ### Knowledge Base Frequently asked questions and troubleshooting guides for all Servolutions products. For the broader questions — POP3 retrieval into Exchange, send connectors and smart hosts, sender addresses in Outlook, OAuth2 — see the Exchange mail flow guides . The SMTP replies Exchange returns to a connector — 421 4.4.1, 421 4.4.2, 451 4.7.0, 452 4.3.1, 530 5.7.1, 550 5.7.1 and the rest — are collected on one page in Exchange SMTP error codes explained . ### POPcon and POPcon PRO ### Exchange Server Configuration Guides - Configuration of Exchange 2013 or 2016 Server - Configuration of Exchange 2010 Server - Configuration of Exchange 2007 Server - Configuration of Exchange 2003 Server - Configuration of Exchange 2000 Server - Configuration of Exchange Server 5.5 ### Frequently Asked Questions - How can I transfer my POPcon configuration settings to a new server? - How to connect to Gmail with modern authentication / OAuth2 - Connect to Microsoft 365 or Outlook online accounts with OAuth2 - "530 5.7.1 Client was not authenticated" error from Exchange - Exchange does not accept emails larger than 10 MB — how to increase the limit - "452 4.3.1 Insufficient system resources" error from Exchange - "550 5.7.1 Unable to relay" error from Exchange - There are .msg files in the POPcon folder with undistributed emails — how to redistribute them - Exchange 2013 SMTP error "451 4.7.0 Temporary server error. Please try again later. PRX" - Emails to unknown Exchange recipients remain stuck in POPcon's queue - Does POPcon work with Exchange 2010, 2007, 2003, 2000, 5.5, SBS editions? - Emails from a mailing list are not distributed correctly - All emails get forwarded to the postmaster because they "do not have local recipients" - POPcon hangs when my virus scanner deletes infected .msg files - Can I trigger mail retrieval from the command line? - Why are emails to unknown recipients in my domain not forwarded to the postmaster? - POPcon downloads email fine but cannot reach my Exchange server - BCC recipients do not receive the email — TO: and CC: recipients do - How to configure POPcon to work with an ISA Server (proxy) - "554 5.5.2 No valid recipients" error from Exchange - POPconAdmin does not work or cannot communicate with the POPcon service - Will I lose emails if Exchange is down when POPcon tries to deliver? - Is there a log of POPcon's actions — where can I find it? - How to get rid of emails stuck in POPcon's delivery queue - All emails are suddenly tagged as SPAM after working fine for a long time - POPcon does not install on my machine — alternative installation method - Exchange SMTP connection unexpectedly closed, or "454 5.7.3 Client does not have permission to submit mail" - How to resend already-downloaded messages - Configuring POPcon for a branch office that handles only part of a domain - How to diagnose malfunctioning antispam blacklist server lookups - "Mail transfer to Exchange failed: Connection to host denied" - "550 5.7.1 Requested action not taken: message refused" from Exchange - POPcon delivers email to both the real recipient AND a catch-all mailbox name - POPcon says it "drops copies" of downloaded email — what does this mean? - "550 5.5.1 user unknown" or "503 5.5.2 need Rcpt command" from Exchange - Can POPcon download email from AOL accounts via IMAP? - Can POPcon download email from Gmail accounts? - "Out of Office" replies go to internal users but not to external internet senders - Why does POPcon need to know the "accepted domains" on the POP3/IMAP config tab? - How to enable non-delivery reports (NDRs) for external senders in Exchange 2003 - Mail does not reach mail-enabled public folders - Only messages under 10 MB come through — does POPcon impose a size limit? - Windows Data Execution Prevention (DEP) is crashing the POPcon antivirus engine - "530 5.7.0 Must issue a STARTTLS command first" or similar STARTTLS error from Exchange - Spam checking takes 30 seconds per message — why is it so slow? - "[blacklist] could not be tested and will not be used" — what does this mean? - Emails to mail-enabled public folders arrive as "posts" instead of emails - How does the POPcon PRO antispam feature work, and why is it not 100% accurate? - Can I use wildcards like `*@spammer.com` in the anti-spam blacklist? - What is the shortest mail download interval POPcon supports? - POPcon moved emails to TOOLARGE or BADMAIL folders — how to resend them - "421 4.4.1 Connection timed out" from Exchange 2007 - Exchange 2007 only accepts one or a few messages at a time from POPcon - "Exchange aborted receiving the message after N bytes" error - Why does my distribution group not accept emails from external senders? - How to forward some accounts to a non-local mailbox on the internet - "552 5.3.4 Header size exceeds fixed maximum size" from Exchange - How to have non-delivery reports (NDRs) sent for unknown users - "421 4.4.2 Message submission rate for this client has exceeded the configured limit" - How to have NDRs sent for emails that are too large instead of moving them to TOOLARGE - "Could not reach Exchange SMTP server — check that IP port 25 is not blocked" - "530 SMTP authentication is required" — what does this mean? - IONOS blocks non-delivery reports and out-of-office messages - I installed CSCatchAll and configured a catch-all account but it does not seem to work at all! What can I check? - How do I configure CSCatchAll? The Administrator utility only allows me to enter a license code. - How to protect Wordpress sites with BotFence - MultiSendcon service won’t start after upgrading — "ChilkatDotNet47.dll or one of its dependencies could not be found" ### ChangeSender - ChangeSender is installed but the sender address is not changing - How to restrict users' choices for Send-As addresses in ChangeSender - How to use the same sender address for two Exchange mailboxes - How to disable the ChangeSender add-in for all users in a terminal server / Citrix environment ### MultiSendcon - "504 5.7.4 Unrecognized authentication type" when using Office 365 SMTP relay - How to manually create the MultiSendcon Send Connector in Exchange Can’t find the answer? Email support — we respond quickly.