SpamAssassin is a mature, widely-deployed open source project that serves as a mail filter to identify Spam. SpamAssassin uses a variety of mechanisms including header and text analysis, Bayesian filtering, DNS blocklists, and collaborative filtering databases. SpamAssassin runs on a server, and filters spam before it reaches your mailbox.
Upgrading spamassassain to version 3.4.0
The release of version 3.4.0 was announced on Feb 11 2014. There are a few optional dependeces while dependency on the following Perl modules were dropped: Net::Ident, IP::Country::Fast and IP::Country. In addition, if you want to install the optional module Geo::IP you have to install GeoIP (here is the package link for slackware users) as well.
Here is how to update quickly:
perl -MCPAN -e shell
cpan> o conf prerequisites_policy ask
cpan> force install Geo::IP IO::Socket::IP Net::Patricia NetAddr::IP
cpan> force install Mail::SpamAssassin Mail::SpamAssassin::Plugin::Razor2