Apache SpamAssassin is an extensible email filter that is used to identify spam. Once identified, the mail can then be optionally tagged as spam for later filtering. It provides a command line tool to perform filtering, a client-server system to filter large volumes of mail, and Mail::SpamAssassin, a set of Perl modules allowing Apache SpamAssassin to be used in a wide variety of email systems.
Chandler is a standards-based "Note-to-Self Organizer" designed for personal and small-group task management and calendaring. It consists of a desktop application and Chandler Hub, a free sharing service and Web application. You can also download and run your own Chandler Server.
The Netty project is an effort to provide an asynchronous, event-driven network application framework and tools for rapid development of maintainable, high-performance, high-scalability protocol servers and clients. In other words, Netty is a NIO client server framework that enables quick and easy development of network applications such as protocol servers and clients. It simplifies and streamlines network programming such as TCP and UDP socket servers.
AtMail is a webmail client. The project aims to provide an elegant client for existing IMAP mailservers, with less bloat and a focus on an intuitive, simple user interface. Features include complete Webmail functionality, address-book support, video mail, an AJAX interface, drag'n'drop, and more.
Echomine Feridian is an easy-to-use Java API that gives you quick and easy access to the XMPP network used in IM services such as Google Talk. The API allows you to communicate with Jabber/XMPP servers for sending and receiving instant messages, presence management, and custom extensions to the XMPP protocol.
Cosmo is the OSAF calendar sharing server. With your favorite calendar program (Chandler, Apple iCal, Mozilla Sunbird, or any other WebDAV or CalDAV enabled client), you can share your calendar with other people by publishing it to Cosmo. Your shared calendars can be subscribed to and updated by anyone, even if they don't have an account on your server. Cosmo provides Atom feeds for shared calendars, so you can track updates in your favorite feed reader and integrate your calendar into your Web site or blog.
The deepOfix Mail Server makes it possible for organizations with minimal technical expertise to have robust server infrastructure. deepOfix offers unprecented ease of use, doesn't require prior GNU/Linux experience and is backed by a full-time development and support team. deepOfix features LDAP-based directory services for user account management, email delivery, distribution lists, and addressbooks. It also includes built in tools for spam and virus control, webmail, and fetching email.