I have set up a Postfix Mailserver, outgoing mail is being sent through a smarthost/relayhost which requires authentification. That works great, internal clients can send to foreign recipients though this relayhost.
However, when an external mail for a local, non-existent user arrives at the server, postfix tries to send a non-delivery notification to the sender. This mail is also sent through the relayhost obviously, but it fails with error 554 5.7.1 : Relay access denied
This gets logged to the mail.log:
Nov 9 10:26:42 mail postfix/local: 6568CC1383: to=<email@example.com>, relay=local, delay=0.13, delays=0.02/0.02/0/0.09, dsn=5.1.1, status=bounced (unknown user: "test") Nov 9 10:26:42 mail postfix/cleanup: 85DF9BFECD: message-id=<20131109092642.85DF9BFECD@mail.mydomain.com> Nov 9 10:26:42 mail postfix/qmgr: 85DF9BFECD: from=<>, size=3066, nrcpt=1 (queue active) Nov 9 10:26:42 mail postfix/bounce: 6568CC1383: sender non-delivery notification: 85DF9BFECD Nov 9 10:26:42 mail postfix/qmgr: 6568CC1383: removed Nov 9 10:26:43 mail postfix/smtp: 85DF9BFECD: to=<firstname.lastname@example.org>, relay=mail.provider.com[18.104.22.168]:587, delay=0.48, delays=0.02/0.01/0.26/0.18, dsn=5.7.1, status=bounced (host mail.provider.com[22.214.171.124] said: 554 5.7.1 <email@example.com>: Relay access denied (in reply to RCPT TO command)) Nov 9 10:26:43 mail postfix/qmgr: 85DF9BFECD: removed
According to this error, I suppose that postfix does not login at the relayhost when sending those bounces. Why? Normal outgoing mail works just fine.
This is how my main.cf looks like: http://pastebin.com/Uu1Dryxy And of course /etc/postfix/sasl_password contains the correct credentials for the relayhost.
Thanks in advance!