Slamming Spam: A Guide for System Administrators

Optional MTA Configuration Changes

The following section shows how to implement certain MTA checks that may reduce both the amount of spam and legitimate messages received. These parameters should be used with caution! The following types of controls are covered here:

• Strict Protocol Adherence

• Eliminating Certain SMTP commands

• Reverse DNS checks

These methods are discussed for each covered MTA in the following sections.

Sendmail

As of Sendmail 8.12, many of the old default settings that were helpful to spammers have been turned off. As a result, the administrator doesn’t need to make as many changes, unless an older version of Sendmail is running or the defaults need to be changed to something more permissive.

Sendmail doesn’t have as many options ...