Sendmail 8.13.3 Programmer's Guide

Introduction
Implementing Filtering Policies
Chapter 16
Implementing Filtering Policies
Milter enables a system administrator to combine third-party filters with
Sendmail to implement a desired mail filtering policy. For example, if a
system administrator wants to perform the following tasks:
• Scan incoming mail for viruses on different platforms.
• Eliminate unsolicited commercial mail message.
• Append a mandatory footer to selected incoming messages
The system administrator can configure the Mail Transport Agent
(MTA) to filter messages first through a server-based anti-virus engine,
then through a large scale antispam service, and finally append the
desired footer if the message still meets the requisite criteria. System
administrators can add or change any filter independently.
You cannot control the overall mail filtering environment but system
administrators can control the mail filtering environment. Particularly,
the system administrator must decide which filters are run, in what
order they are run, and how they communicate with Sendmail. You can
select these parameters, as well as the actions to be taken when a filter
becomes unavailable during Sendmail configuration.