SpamAssassin and all the tools it uses are available for download from the Internet. Perl, the main prerequisite, is included in all major Linux distributions and available for most Unix-like operating systems. It can be downloaded from http://www.perl.org/get.html. The Perl CPAN module is normally used to install SpamAssassin; all that is required is an Internet connection.
This book covers integrating with four of the most popular MTAs—Sendmail, Postfix, Exim, and Qmail. MTA integration is only a small part of this book, and most of this book will be relevant no matter which MTA is in use. SpamAssassin can be integrated with most MTAs.