Chapter 8: SMTP Relaying and Spam Control

Overview

It hasn’t got much Spam in it.

—– Monty Python

No one likes unsolicited bulk e-mail, colloquially known as spam. Well, perhaps someone does, but I’ve yet to meet him or her. Stopping spam depends on two sets of activities: blocking it from reaching your users’ mailboxes and preventing your systems from being used to originate or deliver spam to other systems. In this chapter, I discuss how the Simple Mail Transfer Protocol (SMTP) standard allows delivery to nonlocal recipients (a process called relaying), when relaying is necessary or useful, and how to configure your systems so that they don’t relay spam mail. Once you know how to keep your own servers from being used to originate or forward spam, I explain what you can do to prevent your servers from accepting it.