mail/bogofilter - The NetBSD Packages Collection

Bogofilter is a mail filter that classifies mail as spam or ham
(non-spam) by a statistical analysis of the message's header and
content (body).  It is able to learn from the user's classifications
and corrections.

The statistical technique is known as the Bayesian technique and
its use for spam was first described by Paul Graham in his article
A Plan For Spam.  Gary Robinson, in his weblog Rants, suggests some
refinements for improved discrimination between spam and ham.
Bogofilter's primary algorithm uses the f(w) parameter and the
Fisher inverse chi-square technique that he describes.

Bogofilter is run by an MDA script to classify an incoming message
as spam or ham (using wordlists stored by BerkeleyDB).  Bogofilter
provides processing for plain text and HTML.  It supports multi-part
mime message with decoding of base64, quoted-printable, and
uuencoded text and ignores attachments, such as images.