Plesk server can't send/recieve mail: connect to 127.0.0.1[127.0.0.1]:10024: Connection refused)

Symptoms

• It is not possible to send/receive messages on the Plesk server
• There are a lot of messages stuck in Plesk > Tools & Settings > Mail Queue

• Errors like the ones below can be found in /var/log/maillog:

  CONFIG_TEXT: postfix/error[14359]: ABCD1234567: to=test@example.com, relay=none, delay=0.32, delays=0.32/0/0/0, dsn=4.4.1, status=deferred (delivery temporarily suspended: connect to 127.0.0.1[127.0.0.1]:10024: Connection refused) 

• Amavis service is not running:

  # systemctl status amavis
  amavis.service - LSB: Starts amavisd-new mailfilter
  Loaded: loaded (/etc/init.d/amavis; generated)
  Active: failed (Result: exit-code) since Tue 2024-04-09 12:34:56 -03; 11h ago
  Docs: man:systemd-sysv-generator(8)
  Process: 991 ExecStart=/etc/init.d/amavis start (code=exited, status=1/FAILURE)

Cause

Amavis service is down, but Postfix still tries to use it to filter messages.

Resolution

1. Connect to the server via SSH

2. Restart the Amavis service:

   # systemctl restart amavis

3. Requeue messages with the command below or other methods here:

   # postsuper -r ALL