MyMailBox is an email client written in Java,featuring a user-friendly graphical interface with wizards and internalionalization support.It supports IMAP,POP3 and SMTP.
Nikita is a peer-to-peer PIM. It will offer all the same benefits of the standard PIMS (such as Outlook or Chandler) but will not require a central server. Items can be marked as Calendar, Task, Email, etc... or any combination of those. Silos be gone!
Receptionist is a protocol for email handshaking, which should solve the majority of problems known collectively as "spam" while mitigating the drawbacks of "challenge/response" type implementations.
A plug-in for eclipse workbenth. It provides a group of basic functions to process daily email.