Emails are not delivered to a mailbox in Plesk: DATA REPLY:452:4.2.2 Mailbox full

Symptoms

• Emails are not delivered to a mailbox that is located on the Plesk server (contact@example.net for the purpose of this example)

• Errors that are similar to the following are logged in the /var/log/maillog:

  # [root@server ~]# cat /var/log/maillog | grep "Mailbox full"
  ...
  Jul 30 09:08:45 panel psa-pc-remote[919458]: 7349816000E5: check-quota: stderr: DATA REPLY:452:4.2.2 Mailbox full
  Jul 30 09:08:45 panel postfix/cleanup[3551410]: 7349816000E5: milter-reject: END-OF-MESSAGE from mail-qk1-f197.google.com[209.85.222.197]: 4.2.2 Mailbox full; from=<example@gmail.com> to=<contact@example.net> proto=ESMTP helo=<mail-qk1-f197.google.com>

• Notifications that are configured to be sent from your Plesk server are returned to the mailbox of the main Plesk administrator as a non-delivery notification that has contents which are similar to the following:
  

  CONFIG_TEXT: <contact@example.net>: host 127.0.0.1[127.0.0.1] said: 451 4.5.0 Error in
  processing, id=3361739-19, delivery-notification FAILED: Assert failed: ,
  0, , 0 at /usr/share/perl5/vendor_perl/Amavis/Notify.pm line 706. (in reply
  to end of DATA command)
  Reporting-MTA: dns; panel.example.com
  X-Postfix-Queue-ID: 5C8E6160422B
  X-Postfix-Sender: rfc822; admin@example.com
  Arrival-Date: Thu, 25 Jul 2024 04:46:19 -0500 (CDT)
  Final-Recipient: rfc822; ccontact@example.net
  Original-Recipient: rfc822;contact@example.net
  Action: failed
  Status: 4.5.0
  Remote-MTA: dns; 127.0.0.1
  Diagnostic-Code: smtp; 451 4.5.0 Error in processing, id=3361739-19,
  delivery-notification FAILED: Assert failed: , 0, , 0 at
  /usr/share/perl5/vendor_perl/Amavis/Notify.pm line 706.

• Errors related to the outgoing notification email that are similar to the following are present in /var/log/maillog:
  

  # [root@server ~]# cat /var/log/maillog | grep 5C8E6160422B
  Jul 30 03:49:47 panel postfix/qmgr[1084515]: 5C8E6160422B: from=<admin@example.com>, size=11903, nrcpt=1 (queue active)
  Jul 30 03:49:48 panel postfix/cleanup[3457731]: 530C71600CD4: message-id=<20240725094619.5C8E6160422B@panel.example.com>
  Jul 30 03:49:48 panel postfix/smtp[3457719]: 5C8E6160422B: to=<contact@example.net>, relay=127.0.0.1[127.0.0.1]:10024, delay=428609, delays=428608/0.02/0.02/0.82, dsn=4.5.0, status=deferred (host 127.0.0.1[127.0.0.1] said: 451 4.5.0 Error in processing, id=3377957-12, delivery-notification FAILED: Assert failed: , 0, , 0 at /usr/share/perl5/vendor_perl/Amavis/Notify.pm line 706. (in reply to end of DATA command))
  Jul 30 04:59:47 panel postfix/qmgr[1084515]: 5C8E6160422B: from=<admin@example.com>, size=11903, nrcpt=1 (queue active)
  Jul 30 04:59:48 panel postfix/cleanup[3475031]: F0EEC160013D: message-id=<20240725094619.5C8E6160422B@panel.example.com>
  Jul 30 04:59:48 panel postfix/smtp[3475021]: 5C8E6160422B: to=<contact@example.net>, relay=127.0.0.1[127.0.0.1]:10024, delay=432809, delays=432808/0.02/0.02/1.1, dsn=4.5.0, status=deferred (host 127.0.0.1[127.0.0.1] said: 451 4.5.0 Error in processing, id=3361739-19, delivery-notification FAILED: Assert failed: , 0, , 0 at /usr/share/perl5/vendor_perl/Amavis/Notify.pm line 706. (in reply to end of DATA command))
  Jul 30 04:59:48 panel postfix/qmgr[1084515]: 5C8E6160422B: from=<admin@example.com>, status=expired, returned to sender
  Jul 30 04:59:48 panel postfix/bounce[3475060]: 5C8E6160422B: sender non-delivery notification: 687031600968
  Jul 30 04:59:48 panel postfix/qmgr[1084515]: 5C8E6160422B: removed

Cause

The recipient mailbox on the Plesk server has reached its size limit, due to which it cannot receive more emails.

Resolution

1. Log into Plesk

2. Go to Domains > example.com > Email Addresses > contact@example.net

3. Increase the value in Another size field:

   Note: It is also recommended to delete any old and unusable emails from the mailbox that is affected in order to free up space for new emails.

   

This will allow new emails to get delivered to the affected mailbox.

Additional information

How to delete all or some emails from a mailbox without logging in to the mailbox on a Plesk server?