Unable to send or receive email on the Plesk server: Milter service inet:127.0.0.1:12345: Connection refused

Symptoms

• In an attempt to send or receive an email the process fails with the following error message in the  /var/log/maillog file:

  postfix/smtpd[1742]: warning: connect to Milter service inet:127.0.0.1:12345: Connection refused

Cause

MagicSpam extension was removed previously, however its leftovers exist in Postfix  /etc/postfix/main.cf configuration file.

Resolution

1. Log into the server via SSH.
2. Create a backup for the /etc/postfix/main.cf file:

   # cp -pr /etc/postfix/main.cf /etc/postfix/main.cf.back

3. Using the vi text editor open the /etc/postfix/main.cf file.
4. Find the line below and change it from:

   smtpd_milters = , inet:127.0.0.1:12768 inet:127.0.0.1:12345

   To

   smtpd_milters = , inet:127.0.0.1:12768

5. Save changes.
6. Restart Postfix to apply the changes:

   # service postfix restart