Apache SpamAssassin is a software to help block spam, also known as unsolicited commercial e-mail. If you need help with this software, nobody in the SpamAssassin development team can do this, ONLY your ISP, system administrator or web hosting company can help.

Apache SpamAssassin 3.4.1 represents more than a year of development and nearly 500 tweaks, changes, upgrades and bug fixes over the previous release. Highlights include: Improved automation to help combat spammers that are abusing new top level domains; Tweaks to the SPF support to block more spoofed emails; Increased character set normalization to make rules easier to develop, block more international spam and stop spammers from using alternate character sets to bypass tests; Continued refinement to the native IPv6 support; and Improved Bayesian classification with better debugging and attachment hashing.

Many thanks to the committers, contributors, rule testers, mass checkers,and code testers who have made this release possible.  And please recognize Joe Quinn for stepping up in the role of an assistant Release Manager.

Notable features:
New plugins
There are three new plugins added with this release:
Mail::SpamAssassin::Plugin::TxRep
Mail::SpamAssassin::Plugin::PDFInfo
Mail::SpamAssassin::Plugin::URILocalBL

The TxRep (Reputation) plugin is designed as a substantially improved replacement of the AWL plugin. It adjusts the final message spam score by looking up and taking in consideration the reputation of the sender. It cannot coexist with the old AWL plugin, which must be disabled when the TxRep is loaded.

The PDFInfo plugin helps detecting spam with attached PDF files.

The URILocalBL plugin creates some new rule test types, such as “uri_block_cc”, “uri_block_cidr”, and “uri_block_isp”.  These rules apply to the URIs found in the HTML portion of a message, i.e. <a href=…> markup.

All these three plugins are disabled by default. To enable, uncomment the loadplugin configuration options in file v341.pre, or add them to some local .pre file such as local.pre .

Plugins are documented in their respective man pages.

Notable changes

A new subsystem RegistryBoundaries for recognizing and updating a list of top-level domains and registry boundaries has been introduced, which allows dynamically updating both lists through rule updates instead of having them hard-wired in the code.

A subroutine Node::_normalize has been rewritten. The new behavior is documented with the ‘normalize_charset’ option in the Mail::SpamAssassin::Conf man page. (Bug 7144, Bug 7126, Bug 7133)

Tokenization of UTF-8 -encoded or normalized text has been improved in the Bayes plugin. (Bug 7130, Bug 7135, Bug 7141)

SHA1 digests of all MIME parts (including non-textual) can now be contributed to Bayes tokens, which allows the bayes classifier to assess also the non-textual content. The set of sources of bayes tokens is configurable with a new configuration option ‘bayes_token_sources’ as documented in the Mail::SpamAssassin::Conf man page. (Bug 7115) It is disabled by default for backward compatibility.

Reference
www.wikipedia.com