The hsemail library contains a collection of
Parsec parsers for the grammar defined in RFC2821 and RFC2822. There also is a generic FSM for the SMTP protocol, and several useful utility functions that simplify the manipulation of email or news messages in Haskell.
YateClient is an universal, skinnable VoIP client that supports H.323, SIP, Jingle, and IAX protocols. This software is part of Yate and is available with the Yate packages for Mac.