Postfix is a mail transport agent written by security researcher Wietse Venema. Not surprisingly, Postfix is designed from the ground up to be a highly secure system. It consists of several components, each of which runs with least privilege and none of which trust data from the other without validating it themselves. Despite the extensive security emphasis in the system’s architecture, Postfix is capable of very good performance in normal conditions; because of architectural decisions, it is also fault tolerant and capable of good performance under adverse conditions such as resource starvation. It has become a popular replacement for sendmail because it provides a compatible command-line interface.
This chapter explains how to integrate SpamAssassin into a Postfix-based mail server to perform spam-checking for local recipients or to create a spam-checking mail gateway.
Postfix is a complex piece of software, and, like most MTAs, offers scores of configuration options. This chapter assumes that you are running Postfix 1.1 or 2.x (recommended) and does not cover how to securely install, configure, or operate Postfix itself. For that information, see the Postfix documentation and the book Postfix: The Definitive Guide by Kyle D. Dent (O’Reilly).
different Postfix components play roles in receiving messages from
the Internet. The
master daemon is responsible for the coordination of the components. ...