The Book of
Postfix

Table of Contents

Chapter 1: An Introduction to Postfix

Chapter 2: Preparing Your Host and Environment

Before installing Postfix, you should always verify that your server host can handle an SMTP server. Preparations shows you how to configure the operating system so that you can get to most out of Postfix.

Chapter 3: Mail Server for a Single Domain

The first step in any new Postfix installation is to create a configuration that can receive mail for a single domain. In Mail Server for a single Domain, you will see how to verify that the system works and create a basis for more complicated setups.

Chapter 4:Dial-Up Mail Server for a Singe Domain

You don't need to significantly modify the single-domain setup to get a working dialup configuration. Dial-Up Mail Server shows you these small but important changes so that you .

Chapter 5: Anatomy of Postfix

Wietse Venema says that Postfix is actually a router, one that routes messages instead of IP packets. In Postfix Anatomy, you'll get the big picture of how the Postfix innards interact.

Chapter 6: A Postmaster's Primer to Email

Chapter 7: Understanding Restrictions

Restrictions control SMTP communication. Understanding Restrictions explains how restrictions work.

Chapter 8: Restrictions

Restrictions shows you how to put them to practical use on your system.

Chapter 9: Understanding Checks

Checks do their work based on message content. Understanding *_checks explains how checks work.

Chapter 10: Checks

Checks shows you real-life examples.

Chapter 11: Understanding Filters

Filters delegate SMTP communication management and content control to external applications. This might be necessary if a certain task clearly lies beyond the duties on the MTA (virus filtering is one example). As with restrictions and checks, the discussion of filters breaks down into two chapters: Understanding Filters for a discussion of how filters work.

Chapter 12: Filters

Filters gives you something that you can actually get your hands on.

Chapter 13: Mail Relays

Mail relays transport messages on behalf of other mail servers or clients. In most cases, mail relays are exposed to the Internet, while the other servers sit safely behind a firewall. In addition, you'll see how to make a smart host out of a simple mail relay.

Chapter 14: A Mail Server for Multiple Domains

This chapter describes the two ways that Postfix can handle mail for multiple domains. In addition, you will see how to configure Postfix to query an SQL server instead of looking at static maps.

Chapter 15: SMTP Authentication Primer

SMTP authentication is a system for authenticating mail clients before they relay messages. Because SMTP authentication in Postfix relies on the Cyrus SASL software, Understanding SMTP Authentication shows you how to configure Cyrus SASL before you can use it with Postfix.

Chapter 16: SMTP Authentication

Continuing the discussion of SMTP authentication, Simple Authentication and Security Layer shows you how to configure Postfix for server- and/or client-side authentication.

Chapter 17: Understanding Transport Layer Security

Transport Layer Security (TLS) encrypts the communication layer between Postfix and other hosts. The Postfix implementation of Transport Layer Security requires OpenSSL, so Understanding Transport Layer Security not only shows you how TLS works, but also how to prepare the required certificates.

Chapter 18: Transport Layer Security

This chapter shows you how to set up the Postfix server to offer encryption to other hosts and how to make the Postfix client use it when other servers offer TLS. You will also see how certificate-based relaying works.

Chapter 19: A Company Mail Server

This chapter explains how to configure Postfix to query an LDAP server. In doing so, you will delegate the job of local delivery to an MDA (message delivery agent) and configure a basic Courier IMAP server. In the end, you will have a complete mail system that gets user data from an OpenLDAP server.

Chapter 20: Running Postfix in a chroot Environment

Chrooting Postfix adds another barrier against intrusion. This chapter will tell you how to do that and will give you tipps how you can bring in other applications Postfix might need into the jail too.

Chapter 21: Rate Limiting

Postfix 2.2 and 2.1 snapshots include a new feature for limiting the rate of client connections. Rate limiting is a countertactic for protecting Postfix from SMTP clients that inundate the smtpd daemon with too many connections at once. This chapter illustrates several instances where rate limiting is useful and shows you how to configure it.

Chapter 22: Performance Tuning

Postfix is fast out of the box, but like other packages, you can usually tune it to work even faster. Furthermore, there are situtations where Postfix may not perform as well you expected, whether it is due to hardware or software limitations on the server system or other adverse conditions such as a big influx of spam or undeliverable mail.

This chapter shows you how to find and analyze the most common performance problems.

Appendix A: Installation

Installation contains installation instructions from source code as well as for the Debian and RedHat Linux distributions.

Appendix B: Troubleshooting Postfix

Having trouble with something when you try to modify a configuration? Troubleshooting Postfix gives you some advice for the most frequent gotchas, and gives some general tips for tracking down problems.

Appendix C: CIDR and SMTP Standards Reference

Not everyone can memorize subnets in CIDR notation and SMTP server response codes. We've put them together for you in CIDR notation and response codes.

Glossary

If there's some weird technical term that you don't know, check the Glossary.