Incoming emails are not delivered on Plesk server: /usr/bin/deliverquota: No such file or directory

Symptoms

Incoming emails are not delivered with the following error in /var/log/maillog:

postfix/pipe[7205]: 97AFE18016DEF9: to=john.doe@example.com, relay=plesk_virtual, delay=870, delays=870/0.04/0/0.02, dsn=4.3.0, status=deferred (temporary failure. Command output: /bin/sh: /usr/bin/deliverquota: No such file or directory 4.2.1 Message can not be delivered at this time )

Cause

Misconfiguration of the mail server due to the missed /usr/bin/deliverquota:

# ls -la /usr/bin/deliverquota
ls: cannot access '/usr/bin/deliverquota': No such file or directory

Resolution

1. Connect to the server via SSH.

2. Restore mail server configurations using below command:

   # plesk repair mail -y

3. Re-send all stuck emails from the queue:

   # postqueue -f