Plesk - message cannot be delivered at this time

30.07.2020

A plesk server running postfix shows mail queue entries like these:

[root@server ~]# mailq
50ACA7BA23B2     2646 Wed Jul 29 23:58:42  MAILER-DAEMON
                 (Message can not be delivered at this time)
                 user@domain.com        

or the respective log messages in /var/log/maillog:

Jul 30 13:13:44 srv1 postfix/pipe[19223]: D24A17BA0BD4: to=<user@domain.com>,
relay=plesk_virtual, delay=71918, delays=71914/0/0/3.9, dsn=4.2.1,
status=deferred (Message can not be delivered at this time )

Solution

Log into your Plesk webinterface and check if a password has been set for this email account. If it's missing generate a new one or disable the mailbox.

This bug is known as PPPM-8076 and should be resolved with a future Plesk update.