SpamAssassin is slightly different to most of the software that is used in this book. It is written in a language called Perl, which has its own distribution method called CPAN (Comprehensive Perl Archive Network). CPAN is a large web site of Perl software (normally, Perl modules), and the term CPAN also covers software to download those modules and install them. Though SpamAssassin is provided as a package by many Linux distributions, we recommend that you install it from source rather than use a package.

Most Perl users will build Perl modules using CPAN and experience no difficulties. CPAN can automatically locate and install any dependencies (other components that are required to make the desired component work properly). From a Perl point of view, using CPAN to install Perl modules is like using the rpm command in Linux. The basics are very simple, and once a system is configured, it generally works every time.

However, some people may be put off learning and configuring...