Patrick Nagel wrote:
You could go for bogofilter (purely Bayesian). -- cut -- The solution was inspired by a Gentoo Wiki article (http://www.gentoo-wiki.info/Bogofilter).
If it's not just for personal use, but on a mailserver with quite some users I'd like to happily recommend ASSP. http://assp.sf.net/
It's *not* easy to setup, but after you've gone through all the options and learned about it, it is indeed the most deadly spam killer around.
It's very flexible, with a lot of options. and active development. You can do regex filtering on subject, header, body, data etc. It has a nice web GUI, but you can put several things in different configuration files if you like.
One interesting option e.g. is to do delaying only for emails which have a certain "griplist" score. Another interesting option is the "Test mode", you can run it in front of e.g. postfix and just monitor it without doing any real filtering yet.