Issue Postfix configuration keeps reverting to smtp-amavis content filter when Plesk Email Secruity is not installed

[TimH]

I have 2 new boxes running Centos8 and Plesk Obsidian Version 18.0.28. The box uses Postfix and we have not installed Plesk Email Security.

A couple of days ago email stopped being delivered and both boxes and was found in the queue. After trying to flush the queue and running the basic config checks on the mail server I managed to narrow the issue down to the main configuration file for Postfix /etc/postfix/main.cf

It had the following line in it.

content_filter = smtp-amavis:[127.0.0.1]:10024

However, we do not have amavis installed (/etc/init.d/amavis status).

I commented out this line. Restarted the service (service postfix restart) and then flushed the queue (/usr/sbin/postsuper -r ALL). Success the emails were delivered.

I then logged on following morning and noticed email stuck in the queue again. When opening up/etc/postfix/main.cf I had the following at the bottom of the file

#content_filter = smtp-amavis:[127.0.0.1]:10024
content_filter = smtp-amavis:[127.0.0.1]:10024

So as a temp fix I commented out the new line and repeated steps above. So questions are at this stage:

1. Why is this line even here if Plesk Email Security is not installed?
2. How do I stop the configuration file reverting to the old configuration so that I get a stable mail server?