DKIM for JavaMail is a small JAR that can be easily implemented in existing Java projects using JavaMail for sending DKIM signed emails.
WebMail is a Java Servlet application that gives users WWW access to their IMAP/POP mailboxes. It supports folders, multiple languages, composing messages, MIME and virtual domains.
JSP/Servlets Container based on Tomcat, with some Object-Oriented Applications implemented all in Java Language.
Framemail is a program that lets you check simeotaneously your Yahoo Mail, Gmail, Netscape Mail, Fastmail.FM, and Lycos Mail using frames. More are coming!!!
Jnestor is another majordomo in java
Jnestor is a majordomo developed in java: it can reads an IMAP/POP3 folder (email folder), identifies the elements in it and process them, transforming them as Mantis issues. The software is still experimental, but it passed succesfully the last stages of testing and I hope I will release a stable version soon.
A set of components for the Apache OFBiz ERP. OFBiz_MyHome provides an alternative GUI for OFBiz and adds collaboration, content and document management features (to some extent by integrating external data stores).
icarusWebMail is an open source WebMail, with POP3 and IMAP mailbox support, also supports APOP POP3/SSL POP3/TLS IMAP/SSL contacts lists from LDAP, anti-spam integration, Internationalization (by now es, en, fr), Filters, Drafts, Sent-Folder, Signature.
The ploinMailFactory is a mailing framework that provides extended features like a templating mechanism, multitenancy and localizaion. Internally it uses the commons-email API from Apache.