Mercury is set of e-mail related projects. It currently has implementations of SMTP inbound server and IMAP 4rev1 server. Both are working based on Maildir JavaMail implementation.
Documentation for Mercury can be found here .
For quick start with Mercury check here .
API documentation can be found here .
Every kind of help is more then welcome - from coding, designing to testing (using it) or commenting on it.
Please feel free to send all comments to the forum topics.