This guide is organized in five phases:
An introduction that parallels the introductory material in the second edition of this book. This phase is intended to give you a general overview of sendmail, its parts, modes, roles, and files.
How to download, build, and install sendmail. If you don’t already have the latest version running on your machine, you might have to undertake this step first. This phase steps you through the basic installation.
The meat and potatoes of sendmail are its rules and rule sets. In this phase, we introduce the concept of rules, show how to use them, and provide real-world examples of how to employ them in your own configuration file.
In this phase we first provide an overview of the configuration file, which is central to managing sendmail, then delve down to some of its key components. By the end of this phase you will understand most of the important parts of the configuration file.
To create your own configuration file, you must use the m4 processor. This final phase shows how to use m4 and the steps necessary to create a configuration file using it. We finish with a tour of the many configuration FEATURE( ) commands available.