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"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)

  1. Open Exchange Admin Center.
  2. Go to Mail Flow > Receive Connectors.
  3. Open the Default Frontend [SERVERNAME] connector.
  4. On the Security tab, ensure "Anonymous users" is checked.
  5. 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"
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.
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.
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
POPcon only works with a standard SMTP connection WITHOUT authentication, so allow "Anonymous access" in the "Authentication" dialog

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