It's been said that you aren't a real Unix system
administrator until you've edited a sendmail.cf file.
It's also been said that you're crazy if you've attempted to do so twice.
sendmail is an incredibly powerful mail
program. It's also incredibly difficult to learn and understand. Any
program whose definitive reference (sendmail, by
Bryan Costales and Eric Allman, published by O'Reilly) is 1,050 pages long scares most people
off. Information on the sendmail reference is
contained in the bibliography at the end of this book.
Fortunately, new versions of sendmail are different. You no longer need to
directly edit the cryptic sendmail.cf file; the
new version provides a configuration utility that will create the
sendmail.cf file for you based on much simpler macro
files. You do not need to understand the
complex syntax of the sendmail.cf file; the macro files
don't require you to. Instead, you need only list items, such as the name of
features you wish to include in your configuration, and specify some of the
parameters that determine how that feature operates. A traditional
Unix utility called m4 then takes your
macro configuration data and mixes it with the data it reads from template
files containing the actual sendmail.cf syntax, to
produce your sendmail.cf file.
In this chapter we introduce sendmail and describe
how to install, configure and test it, using the Virtual Brewery as an
example. If the information presented here helps make the task of
configuring sendmail less daunting for you, we hope
you'll gain the confidence to tackle more complex configurations on