How to block spam/email by subject for the entire server

Introduction

It is possible to block messages from reaching your user's inbox by creating a system-level filter for the entire server. Use the following guide to learn how.

Procedure

Login to the server via SSH as the root user

Create the filter file with the following command:

touch /usr/local/cpanel/etc/exim/sysfilter/options/block_subjects.conf

Edit the file with a text editor of your choice and put the following contents within:

if ("$h_subject:" contains "example subject")
then fail
endif

if ("$h_subject:" contains "another example subject")
then fail
endif

Edit the contents of the file so that it blocks your desired subjects

Login to WHM as the root user and navigate to the following location:

WHM >> Home >> Service Configuration >> Exim Configuration Manager

Click on the Filters tab

Verify that the custom filter that you just created is enabled, or disable the filter if you desire to do so.

Supplemental Documentation

cPanel Docs - How to Customize the Exim System Filter File

Exim Docs - Chapter 3: Exim Filter Files