Apache SpamAssassin is an extensible email filter that is used to identify spam. Once identified, the mail can then be optionally tagged as spam for later filtering. It provides a command line tool to perform filtering, a client-server system to filter large volumes of mail, and Mail::SpamAssassin, a set of Perl modules allowing Apache SpamAssassin to be used in a wide variety of email systems.

SpamAssassin will use tests to check mail headers, the body, IP Addresses and checksums to locate patterns that indicate SPAM. So SpamAssassin will use pattern-based scores for checking patters that are found in headers, the body or attachments and it will use network-based tests that use DNS lookups or access RBL lists.

The Haraka mail server is able to use common plugins like Spamassassin to enhance the features that it provides. Using Spamassassin with Haraka is easy to do and reduces the normal resources used by a mail server.

"Current Spam fighting techniques like for example SpamAssassin are reactive. SpamAssassin uses a rule based approach and a Bayesian filter.[...]Bayesian filtering requires to collect a rather large amount of mail messages before messages can be filtered. This illustrates that reactive Spam fighting is no real solution."

This howto describes one way to build a scalable, secure, full-featured mail platform. It offers virtual hosting of mailboxes in maildir format with support for quotas and server-side filtering, domain aliasing, address aliasing, address forwarding, catchall addresses. Relaying is secured with STARTTLS and SMTP-AUTH.

Estimates say that spam makes now up for 80 - 90% of all emails, and many mail servers have difficulties in managing the additional load caused by the latest spam, and spam filters such as SpamAssassin do not recognize large parts of that spam as they did before.

Once you have set up Spamassassin so it is working and you have run it for some time you may want to tune it to provide automatic whitelists and blacklists. The whitelist will provide a way to insure that the mail from a particular source will never get rejected.

This tutorial describes how to scan emails for image spam with FuzzyOCR on a Fedora 12 server. FuzzyOCR is a plugin for SpamAssassin which is aimed at unsolicited bulk mail containing images as the main content carrier. Using different methods, it analyzes the content and properties of images to distinguish between normal mails (ham) and spam mails.

This tutorial describes how to scan emails for image spam with FuzzyOCR on a Debian Lenny server. FuzzyOCR is a plugin for SpamAssassin which is aimed at unsolicited bulk mail containing images as the main content carrier. Using different methods, it analyzes the content and properties of images to distinguish between normal mails (ham) and spam mails.