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

Introduction

A system-level filter can block email for an entire server based on the subject line. This article provides the steps to create such a filter.

Procedure

1. Access the server's command line as the 'root' user via SSH or "Terminal" in WHM.
2. Create the filter file.

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

3. Open the file in your preferred text editor.
4. Add the following to the text file.

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

   Please note that "example subject" must be replaced with the text that should be matched. You can also add additional if/then/endif statements for each additional text string you want matched.
5. Log in to WHM as the ‘root’ user.
6. Navigate to "Home / Service Configuration / Exim Configuration Manager."
7. Click on the Filters tab.
8. Verify that the custom filter just created is enabled.
9. Click the "Save" button.

Additional resources

How to Customize the Exim System Filter File

Exim Internet Mailer: Chapter 3 - Exim Filter Files