Mail stuck in queue on Plesk server: delivery temporarily suspended: connect to 127.0.0.1[127.0.0.1]:10024: Connection refused

Symptoms

• Mail stuck in queue on Plesk server with the following error messages in /var/log/maillog:

  CONFIG_TEXT: name postfix/error[14531]: 8954F66E14A4: to=jdoe@example.com, relay=none, delay=25755, delays=25754/0.07/0/0, dsn=4.4.1, status=deferred (delivery temporarily suspended: connect to 127.0.0.1[127.0.0.1]:10024: Connection refused)

• Plesk Email Security is installed on the server, however Amavis service fails to start with the following errors:

  CONFIG_TEXT:  systemd[1]: Starting Amavis mail content checker...
  name amavisd[1507]: The value of variable $myhostname is "name", but should have been
  name amavisd[1507]: a fully qualified domain name; perhaps uname(3) did not provide such.
  name amavisd[1507]: You must explicitly assign a FQDN of this host to variable $myhostname
  name amavisd[1507]: in amavisd.conf, or fix what uname(3) provides as a host's network name!
  name systemd[1]: amavisd.service: control process exited, code=exited status=255
  name systemd[1]: Failed to start Amavis mail content checker.
  name systemd[1]: Unit amavisd.service entered failed state.

Cause

Hostname has been changed manually on the system:

# hostname
example

Resolution

1. Log into Plesk > Tools & Settings > Server Settings and change Full hostname to temporary one (for example temp.server.example.com) and press OK

2. Open Server Settings and change Full hostname back to original one again and press OK
3. Start amavisd service:

   # service amavisd start