Forwarded emails rejected by provider smtp relay

Many webspace and email server providers now block emails with the wrong FROM addresses even though your Exchange server authenticates via SMTP AUTH with them. This is not normally a problem since all your regular users will be in the right domain – the one that your login to that provider is associated with.

But there is one special case: You can set Exchange to automatically forward incoming emails to an external “contact” in the configuration options of the Exchange mailbox. It’s a nice feature if you want incoming emails (both from external and domain-internal sources) to be copied to an outside mailbox for sync to a smartphone for example.

But: Exchange uses the original (external!) sender’s email address as the sender address in the forwarded email, not the email of the person forwarding. These messages can then get blocked by your provider because the sender address is outside of your domain.

To solve this problem, at least for all users of MultiSendcon, we introduced a new feature in MultiSendcon that allows sending out these emails using a general admin or postmaster email address in the SMTP FROM envelope instead of the one given by Exchange (the external address that would get rejected). The special feature that we added was an option to only replace the smtp from envelope but not the FROM: email header that shows up in the email when it’s later read.

How to use it in MultiSendcon:

  • In addition to the individual provider relay servers you already have in MultiSendcon you need to add one more account as a “catch-all”
  • Make sure to add this account at then end of the account list so that it only gets used when non of the regular accounts fits the sender address.
  • Make this catch-all account apply to “ALL senders” (and all recipients) and switch on the “sender replacement” feature but with the special option to only replace the smtp envelope.

This is how the account could look like:


Any questions? Feel free to ask us any time!