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= What is SpamAssassin? =

Spam``Assassin is a mail filter to identify spam. It is an intelligent email filter which uses a diverse range of tests to identify unsolicited bulk email, more commonly known as [[Spam]]. These tests are applied to email headers and content to classify email using advanced statistical methods.  In addition, Spam``Assassin has a modular architecture that allows other technologies to be quickly wielded against spam and is designed for easy integration into virtually any email system.

'''Want to learn more?'''

  * Questions about using SpamAssassin can be asked on the SpamAssassin-Users MailingLists.  However, please note AskingAboutIntegrations.
  * '''BooksAboutSpamAssassin''': Published books that discuss Spam``Assassin.
  
= Advantages =

Spam``Assassin's practical multi-technique approach, modularity, and extensibility continue to give it an advantage over other anti-spam systems.  Due to these advantages, Spam``Assassin is widely used in all aspects of email management.  You can readily find Spam``Assassin in use in both email clients and servers, on many different operating systems, filtering incoming as well as outgoing email, and implementing a very broad range of policy actions.  These installations include service providers, businesses, not-for-profit and educational organizations, and end-user systems.  Spam``Assassin also forms the basis for numerous commercial anti-spam products available on the market today.

= How it works =
 
This flexible and powerful set of Perl programs, unlike older spam filtering approaches, uses the combined score from multiple types of checks to determine if a given message is spam.

Its primary features are:
  * Header tests
  * Body phrase tests. For more information, see SpamAssassinRules.
  * Bayesian filtering (BayesFaq)
  * Automatic address whitelist/blacklist (AutoWhitelist)
  * Manual address whitelist/blacklist (ManualWhitelist)
  * Collaborative spam identification databases (DCC, Pyzor, Razor2); See UsingNetworkTests.
  * DNS Blocklists, also known as "RBLs" or "Realtime Blackhole Lists". See DnsBlocklists
  * Character sets and locales
 
Even though any one of these tests might, by themselves, mis-identify a [[Ham]] or [[Spam]], their combined score is terribly difficult to fool.

= About the Apache Software Foundation =

Spam``Assassin is an Apache Software Foundation project and is released under the Apache License. The Apache Software Foundation provides organizational, legal, and financial support for a broad range of open source software projects.  As a US 501(c)(3) public charity, the Foundation provides an established framework for contributions of both intellectual property and funding for the support of open source software development.  Through a collaborative and meritocratic development process, Apache projects deliver enterprise-grade, freely available software products for the public benefit, attracting large communities of users and enabling future innovation, both commercial and individual, through its pragmatic Apache License.
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