dr.moensted's Eudora Internet Mail Server page
this page is no longer updated, all plugins removed may 16. 2003

EIMS used to be called AIMS (Apple Internet Mail Server) and be free, now however it's an commercial product from Eudora.

EIMS can be be found here.
The author (Glenn Anderson) has a webpage with cool stuff here.
There is a mailing list but no web-archive, so you might find this helpful.
There is a FAQ.
Tom Shaw has a EIMS filter page here.
Also take a look at the Simpel Text Filter!