Apache SpamAssassin is a configurable, Perl-based open source software application used for e-mail spam filtering. The program uses Domain Name System (DNS)-based and checksum-based spam detection, Bayesian filtering, external programs, blacklists, and online databases. Apache SpamAssassin can be integrated with the mail server to automatically filter all mail for a site or individual user, and integrates with several mail programs.
The program received the 2007 InfoWorld Bossie Awards as Best of Open Source Software Award in the Anti-spam Category; 2006 Datamation Product of the Year; 2006 Linux New Media Award for 'Best Linux-based Anti-spam Solution'; and 2003 OSDir.com Editor's Choice.
Justin Mason started the Apache SpamAssassin project on SourceForge.net in 2001, and it was originally licensed under the same terms as Perl. In 2004, Apache SpamAssassin moved to the Apache Software License as part of joining the Apache Software Foundation (ASF).
Cisco's Daniel Quinlan led the work to bring Apache SpamAssassin into the ASF, and he served as Apache SpamAssassin’s project leader for two years. Quinlan, and Cisco’s Michael Parker, Henry Stern, and Duncan Findlay are major contributors to the Apache SpamAssassin project, and this team has contributed more code back to Apache SpamAssassin than have employees of any other anti-spam company.
Michael Parker remains one of the project management committee members, helping lead the Apache SpamAssassin project’s code development activities and with Duncan Findlay, provides updates and improvements to the upstream Apache SpamAssassin project. Parker’s and Findlay’s contributions include a plugin interface for the message check functionality, libspamc updates, and a reuse plugin to facilitate easy reuse of historic rule hits.
In addition Henry Stern, currently a Committer Emeritus, developed the Apache SpamAssassin rule-scoring system. Stern also contributed to SURBL and URIBL blocklists, two of Apache SpamAssassin's most important partners in rapid response to new spam campaigns. Cisco thought leaders remain as actively involved in Apache SpamAssassin's continued development and maintenance as they were in the original technical innovation.