The remainder of the chapter explains how to set up a backend for SMTP authentication — a choice between saslauthd and other options — and the following chapter then explains how to configure Postfix to use it. This approach is typical of The Book of Postfix, which tackles many topics with paired chapters, the first covering background, theory and any ancillary systems and the second covering the actual Postifx configuration. It also emphasises progressive implementation accompanied by testing, which is most reassuring when modifying production servers.
Other chapters in Part III, "Advanced Configurations", cover running Postfix chrooted, using TLS (two chapters), mail gateways and multiple domains. There's also a chapter that works through building a complete mail system for an organisation. Part IV covers tuning and the appendices cover installing Postfix (for Debian or Redhat Linux, or from source) and troubleshooting.
Moving backwards, the hundred and twenty pages in part II cover content controls. Some basic postmaster background is followed by pairs of chapters on each of message transfer restrictions, built-in content filters, and external content filters. I've been working through these, improving my anti-spam controls, and they're proving really helpful; my next step will be implementing amavisd-new.
Part I explains how to set up a host to run Postfix, with ancillary services such as DNS, NTP and syslog, then how to set up a simple single domain configuration, either on a permanently connected machine or on a dialup machine. It then gives a brief description of Postfix's basic anatomy. Part I is concise — just fifty pages — but it offers everything most people will need for a basic setup.
There's no cruft in The Book of Postfix: it's a fairly chunky book, but none of it is padding. Excerpts from configuration files include just the right amount of context and the diagrams (and a very few screenshots) are integrated with the text and tightly focused. Given the scope, it's probably overkill for basic Postfix users, though the first fifty pages would make an excellent "getting started" guide for them.
There are some omissions. There's no general explanation of how the master.cf file works, for example, or of rewriting — neither "masquerading" nor "canonical" appear in the index or glossary. The "Anatomy of Postfix" chapter could definitely have been more comprehensive. But these are minor flaws.
How does The Book of Postfix compare with the O'Reilly book Postfix: the Definitive Guide? The Book of Postfix is nearly twice the length and provides much more detailed step-by-step explanations and more on ancillary systems — it explains how to set up backends for SMTP authentication, for example, rather than just telling you that you need one.
I highly recommend The Book of Postfix to anyone using Postfix and wanting to do more than the basics with it.
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