This is a mail filter which uses the Bayes algorithm as explained in Paul Graham's article "A Plan for Spam". It aims to be smaller, faster, and more versatile than other filters. The implementation is ANSI C and uses POSIX functions. Supported platforms are (in theory) all POSIX systems. It is independent from external programs and libraries, supports multiple database formats (flat files, libdb, and MySQL), and uses efficient zero-copy processing. SpamAssassin style passthru mode and headers are supported.