sendmail has long been the most widely used mail transport agent in the world. It was routing mail before the Internet existed as such and continues to form the backbone of many of the largest mail servers on the Net today. This chapter explains how to integrate SpamAssassin into a sendmail-based mail server to perform spam-checking for local recipients or to create a spam-checking mail gateway.
sendmail is a complex piece of software and can have several security implications for systems on which it runs. You should always run the most up-to-date version of sendmail and keep track of new bug reports and security advisories. This chapter assumes that you are running the latest release of sendmail—Version 8.12—and does not cover how to securely install, configure, or operate sendmail itself. For that information, see the sendmail documentation and the book sendmail by Bryan Costales and Eric Allman (O’Reilly).
The easiest way to add SpamAssassin to a sendmail system is to configure sendmail to use procmail as its local delivery agent, and to add a procmail recipe for spam-tagging to /etc/procmailrc. The advantages of this approach are
It’s very easy to set up.
You can run
spamd, and the procmail recipe can use
spamc for faster spam-checking.
User preference files, autowhitelists, and Bayesian databases can be used.
There are also some disadvantages:
sendmail must complete the SMTP transaction and ...