Postfix: The Definitive Guide Author: Kyle D. Dent Pages: 260 Publisher: O'Reilly ISBN: 0-596-00212-2 Summary: A useful guide for managing Postfix mail systems. Review Date: 11 September, 2004

I first came across Postfix a few years back when my company was having problems with sendmail on the mail forwarding servers for our rapidly growing web hosting platform. Advertised as a secure and fast 'drop-in' replacement for sendmail, Postfix was intriguing, and rapidly became a flexible, reliable, and much appreciated piece of our infrastructure. In recent months amidst the ever-increasing plague of computer viruses, worms, and spam, log analysis on one of our forwarders showed in one instance that our dual-CPU Pentium-III machine with a single SCSI disk for the Postfix queue had handled over 200,000 messages in a single day. Needless to say, we were impressed.

So when I learned that O'Reilly had a book on Postfix in the wings, naturally I was eager to get my hands on a copy. To this point I had relied on man pages, the Postfix mailing list, and source documentation, which has been adequate, but I've longed for something to give me a better "big picture" of Postfix. Fortunately Postfix: The Definitive Guide does a very good job at that. That's not to say that the book is perfect, however. As a "Definitive Guide", I found some areas of the book lacking, but overall it's a great book for anyone who would like to come up to speed with Postfix. The table of contents at the book's website gives a good picture of the range of topics covered. Following are some of my thoughts on the highlights of the book.

The first couple of chapters are intended to provide an introduction to Postfix, and Internet email delivery in general. The material is informative and helpful, and provides a good introduction to Postfix, but glosses over a lot of details with respect to Internet email delivery. In comparison, the introductory material in The Bat Book is much more comprehensive and well-written.

Chapter three is where things started to get interesting for me. Again, up until I read the book, piecing together the big picture of Postfix was a fair challenge. Having read this chapter on Postfix architecture, I had a much better understanding of how all the different parts fit together, and the various routes a given message could flow through a Postfix system. This chapter provides an excellent foundation on which all the other parts of the book fit.

Chapters four through six are also very helpful. Here you learn how to use the various tools necessary for managing a Postfix system. This includes generating and configuring lookup maps, working with the configuration files, setting up Postfix to run chrooted, queue management, and relevant DNS issues. With the foundation given in chapter three, chapters 4-6 provide the various basic tools for building and managing the framework of your Postfix system.

The rest of the book (chapters seven through fifteen) covers various aspects of configuring your Postfix system. Here you find out how to manage local delivery, virtual email, mail relaying, manage mailing lists, dealing with spam, security, content filtering, and utilizing external databases such as MySQL and LDAP. By and large these chapters provide a lot of good information, and cover most of what the average sysadmin will have to deal with on a regular basis in managing their Postfix system. Examples are plentiful, and are clear and easy to follow. I especially liked the chapter on dealing with spam. Spam filtering on Postfix can be complex and challenging due to Postfix's flexibility in this area, but the book does a very good job in sorting out how it all works.

The book has four appendices:

• Configuration parameter reference. This appendix outilines each of the various parameters you can use (in main.cf) to configure your Postfix system. Each parameter is given a short description, and a very simple example of its usage. As it stands, this appendix is very useful, but it could be so much more so if it were a little less concise.
• Postfix command reference. This appendix gives a simple description of each of the Postfix commands (e.g., postqueue, postmap, etc.) and refers the reader to the man page for each command for more details. Again, some more meat here would be welcome.
• Installing Postfix. This appendix outlines the process for compiling and installing Postfix. I like the fact that the author put this section in an appendix as opposed to the first chapter of the book.
• Frequently asked questions. This appendix offers a few common questions and problems encountered by Postfix users, and offers answers to each. This section also could use some more meat.

So that should give you an idea of what the book covers, but the real question of any technical book is it's usefulness.

About the time I read this book I had to prepare for a presentation on Postfix for a local LUG meeting. The book was a very welcome help in preparing my presentation, and its clear examples served well to help me understand some of the features I have less experience with, but which I wanted to cover in my presentation. So in that aspect the book was very useful.

As far as its usefulness in my day-to-day work as a sysadmin, I find myself turning more often to the recently updated Postfix website these days, than I do to the book. But that's not to say the book isn't useful. I think the book would be fantastic for anyone starting out with Postfix, or for someone (like me) who has experience with Postfix, but who wants a better "big picture" of the whole thing. The book serves as a better tutorial than reference, whereas the Postfix website is better in terms of reference material. Postfix, as the authors admit, is a rapidly moving target to cover in a book like this, so for coverage on the latest features added to Postfix, you'd be better served by consulting the website.

The book is definitely a good guide to Postfix, but I don't think it's quite "definitive." In a definitive work I would really like to see an entire chapter devoted to tuning a Postfix setup, with discussion of configuration tuning, as well as optimal hardware layout. I've also tinkered a bit with the Postfix source code (which I might add is a beautiful set of code), and in a definitive work, it would be nice to get coverage of the various libraries the Postfix author uses extensively in the code (vstring in particular), and information on the interfaces expected of lookup map modules. Something of a "hacker's guide," perhaps.

In summary, Postfix: The Definitive Guide provides an excellent introduction and tutorial to the main features of the Postfix mail system, but leaves something to be desired as far as being a reference volume.

Overall Rating: 8/10