Chapter 25. Configuring Email Services

IN THIS CHAPTER

• Introduction to SMTP

• Mail Transfer Agents (MTAs) and Mail User Agents (MUAs)

• Configuring Basic Email Services with Sendmail

• Understanding Relaying

• Introduction to POP3

• Configuring a POP3 Server with Qpopper

• Configuring an IMAP Server with IMAP-UW

• Email for Standalone Workstations

• Filtering Junk Mail with Procmail and SpamAssassin

• A Look at Some Sendmail Replacements

What's the Internet without email? Probably not even the Web, with its flashy graphics and its commercial opportunities, has quite the usefulness and cachet of the Internet's oldest application, electronic mail. Every UNIX server in the world has email capabilities built into itnot just the capability for users to send and receive mail, but for the system itself to act as a full-fledged mail server. FreeBSD is no exception.

The catch is that configuring Sendmail, the venerable SMTP server application that forms the email backbone of UNIX and the Internet, is perhaps the most daunting system administration task you'll face. After all, Sendmail is perhaps unique among server software in that it has a config file for its config file. But don't worrythis chapter outlines and gives you a solid grounding in the use of Sendmail and the basics of the skills you'll need to master as an email administrator. You learn how to configure and manage the mail server for secure and reliable performance, but you're spared the exhaustive coverage of details that could make Sendmail seem overwhelming or needlessly complex.

This chapter also covers another side of email: POP and IMAP. These are the protocols remote clients use to receive email. Fortunately, their use is nowhere near as complicated as Sendmail, even when you're configuring them for secure (encrypted) operation.

Finally, the chapter outlines some alternatives to Sendmail itself, explaining how to switch to them if you decide administering Sendmail isn't worth the headache. You'll also see how to configure your mail server to filter unsolicited junk mailunpopularly known as spamusing third-party tools such as Procmail and SpamAssassin.