The Apache James Protocols Project delivers a lightweight, and highly extensible framework for mail protocols implementations.
The framework was build as a generic one, so its not bound to any socket implementation. This make it possible to use it with NIO or IO Frameworks.
You can download James Protocols official release from the download page.
The framework is currently used by James Server in conjunction with Netty to provide a high performance and extensible SMTP, POP3 and IMAP4 Server.
At the moment those 3 standard mail protocols are included, but others will follow.
The source code page contains information on how to develop with James Protocols.
You can also read more on the way the James Server uses James Protocols to Hook SMTP.
Apache James is a project of The Apache Software Foundation (ASF) which encourages a collaborative, consensus-based development process under an open software license.
The ASF maintains other Java projects which may also be of interest. These are detailed on the ASF Projects page.
We recommended that users of James products subscribe to the James users mailing list.