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The primary reason for this book, the second edition of sendmail , is the release of version 8.8 of the sendmail program. V8.8 sendmail differs so significantly from earlier versions that a complete rewrite was called for.

Also, since the publication of the first edition, feedback from around the world made it clear that a number of improvements could be made. Some readers felt, for example, that the original offered too little in the way of real-world help, and that it lacked an annotated, major configuration file. Other readers offered suggestions of ways to make the book clearer. Some of these were minor but others, like the treatment of options, required extensive rewriting. One of the most noticeable changes between this edition and the original is the addition of section numbers and their attendant cross referencing.


King Gordias of Phrygia once created a knot so tangled that no one could undo it. The Gordian Knot stayed just that, or so the story says, until Alexander the Great came along and took a different approach to untying knots. It would be nice if the knot that is sendmail could be undone with one quick stroke of fresh insight, but, alas, it cannot. Instead, a more mundane approach must be taken, so in this book we untie it the hard way, one strand at a time.

But, you may ask, "Why the effort? Doesn't sendmail predate the dawn of computing time? Isn't it time to replace it with something new, something better, something modern?" Not so. Age has brought sendmail maturity and reliability. The sendmail program has withstood the test of time because it is more than just a program, it is a philosophy: a general-purpose, internetwork mail-routing facility with the flexibility and configurability to solve the mail-routing needs of all sites large or small, complex or simple.

These strengths of sendmail are also its weaknesses. Configurability has bred complexity. The sendmail program is difficult to configure and even more difficult to understand. Its configuration file, for example, can be positively frightening. But don't despair. With this book in hand, you should be able to configure sendmail to meet any need and bring the days of the sendmail guru to an end.