POP Server and MetaCard

[David Bovill]

I need to process incoming email with my own scripts:  ideally with
Metacard. Does anyone have any information on preferably free POP mail
servers for Mac/UNIX which I could extend using MetaCard CGI's?

Or is anyone planning on writing/getting involved in writing a basic POP
server in MetaCard? Any information regarding these options would be much
appreciated.