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I am running a Postfix MTA. Fetchmail is used to get mails from several POP3 accounts.

The problem is: If a mail cannot be delivered, e.g. because it exceeds the size limit of the mailbox, a bounce message is sent. However, the bounce mail uses the mail address of the account on the Postfix server, not the original mail address on the POP3 server. This means, the sender cannot recognize that the mail has not been delivered, and he gets bounce messages from a different mail address that he cannot relate to any sent message, so he rejects them. This leads to an endless exchange of bounce messages that are bounced back from the original sender.

What I need: How do I change the mail address of the bounce messages?


  • sender@sender.com sends a mail to receiverpop@pop3server.com
  • Postfix on postfixserver.com fetches this mail from pop3server.com and tries to deliver it to receiverpostfix@postfixserver.com
  • mail is too large, so it is rejected
  • bounce message to sender@sender.com, that the mail from receiverpostfix@postfixserver.com could not be delivered
  • sender@sender.com is confused, he never sent a mail to receiverpostfix@postfixserver.com
  • the bounce message should have receiverpop@pop3server.com as the sender address

Any suggestions? Thank you!

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