Useful commands
postfix reload # Gracefully reload configs postfix log # Monitor in real-time: tail -f /var/log/maillog
dovecot unix - n n - - pipe flags=DRhu user=vmail argv=/usr/libexec/dovecot/dovecot-lda -f $sender -d $user@$domain -o plugin/quota=maildir:User quota -d
Restart Postfix: sudo systemctl restart postfix
Nov 15 10:35:22 server postfix/cleanup[12345]: ABCD123: message-id=<...> Nov 15 10:35:22 server postfix/qmgr[12346]: ABCD123: from=user@example.com, size=1234, nrcpt=1 Nov 15 10:35:23 server postfix/pipe[12350]: ABCD123: to=user@domain.com, relay=delivery, delay=0.2, status=deferred (delivery temporarily suspended: unknown mail transport error)
: The most descriptive error is usually further back in the logs. Look at /var/log/mail.log /var/log/syslog
In the world of email server administration, clarity is king. Error messages ideally point directly to a misconfiguration, a full disk, or a refused connection. However, system administrators occasionally face a frustratingly vague adversary: delivery temporarily suspended: unknown mail transport error . When paired with postfix/update (often observed in logs referencing postfix/trivial-rewrite or postfix/qmgr ), this message indicates a scenario where Postfix knows something is wrong, but cannot—or will not—specify the exact cause.
8.5
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