jwma (java webmail app) uses jakarta mail (formerly javamail) to provide access to an imap email store. Multiple users can authenticate, read, send and manipulate email storage and persist a list of contacts, email identities and their own individual preferences.
It works with email stored in mbox or maildir format or stored in a derby database; it has been tested with dovecot.james and exim4.
...It includes the ability to securely share information with co-workers either individually or via assigned groups. Twiggi features the following modules: IMAP webmail, calendar, todolist and more...
Engroup is the web enterprise groupware promotes various collaboration methods plus adding company business management modules. Features are included: CRM, HRM, Document Management, Project Management, Chat, Wiki, Forum, News, Todo.
mail2m (Mail 2 Many) is a tiny simple bulk mail sender, designed to send a simple html mail to a group of friends. Recipients list can contain up to 200 (and more ?) recipients. No database and only basic smtp configuration is needed.
CPO is a tool written in Java that manages newsletters. It's focused on corporate needs (privacy, scalability, bounce count, opt-in & out, newsletter statistics).
justwork.groupware is a teamwork suite. Feature list includes address book, calendar, email client, portal integration, project and task management, etc. Project is developed in Java(tm) is based on J2EE(tm) for scalability and maintainance reasons.