Best spam filter?

[The Stinger]

My boss needs a new spam filter, he has like 7 different email adresses and hes running Eudora 8(Thunderbird).

[Crosma]

SpamAssassin (http://spamassassin.apache.org/). It's designed to be server-side and can be easily used with all sorts of mail servers. Or it can be client-side and also use Bayesian filtering. Most of the filtering is done by a rule-set, which the daemon will update automatically.

[The Stinger]

Thanks for the tip.
I've downloaded SpamFu, which is a windows pop proxy and uses SpamAssassin as filtering.