Linux Babe published a guide about setting up SpamAssassin on CentOS or RHEL to block email spam.

Set Up SpamAssassin on CentOS/RHEL to Block Email Spam

Previously we discussed 7 effective methods for blocking email spam with Postfix SMTP server. In this tutorial, we are going to learn how to use SpamAssassin (SA) to detect spam on CentOS/RHEL mail server. SpamAssassin is a free, open-source, flexible and powerful spam-fighting tool. SpamAssassin is a score-based system.

Set Up SpamAssassin on CentOS/RHEL to Block Email Spam