Dwarf

Dwarf: "Dwarf Mail Server - product overview
Dwarf Mail Server is a full-featured mail server developed on the Java? platform, implementing SMTP, POP3 and IMAP4rev1 protocols.
It provides support for rich application message processing via pluggable mail filters and agents, as well as full handling of virtual domains for the SMTP/POP3/IMAP4 protocols, and is free of charge for the binary redistribution.
Since the server is based on the Dwarf framework, it also shares its common design principles and features - simplicity, high modularity and extensibility, authentication and authorization, XML-based configuration, logging and remote management.
Features

* ESMTP, POP3 and IMAP4rev1 implementation
* application logic layer provided by mail filters and agents
* virtual mail hosts in SMTP/POP3/IMAP4 server
* application-independent authentication and authorization
* sample JSP-based webmail interface"