Building a complete email system with spam and antivirus protection is not as hard as you might think. This guide will walk you through installing and configuring everything you need for sending and receiving email, filtering spam, and scanning for viruses in email.
For our system, we´ll use the Postfix mail transport agent (MTA); Dovecot, a secure, open source IMAP and POP3 server for Linux/Unix-like systems; SquirrelMail, a standards-based Webmail package written in PHP 4; SpamAssassin, a powerful open source spam filter; and ClamAV, a GPLed virus scanner. To tie everything together we´ll use amavisd-new, a high-performance interface between MTAs and content checkers such as virus scanners and spam filters.
The system will be configured so that users will have POP, secure POP, IMAP, and secure IMAP (IMAPS) access, and will also be able to access their email from the Web using SquirrelMail. Every email sent or received will be scanned for viruses and checked for possible spam content.