GNU Mailutils is a rich and powerful protocol-independent mail framework. It contains a series of useful mail libraries, clients, and servers. These are the primary mail utilities for the GNU system. The central library is capable of handling electronic mail in various mailbox formats and protocols, both local and remote. Specifically, this project contains a POP3 server, an IMAP4 server, and a Sieve mail filter. It also provides a POSIX "mailx" client and a collection of other handy tools.
KONSEC Kolab Server is a highly scalable, cluster-capable messaging and collaboration server that is based on the outstanding open source project, Kroupware. The KONSEC Konnektor is a simple client extension that gives Outlook complete group functionality through the Kolab Server, which employs the open standard IMAP together with ACLs, thus enabling you to collaborate in a unique mixed Windows/Linux environment.
sYnergy is a Web-based groupware and communication solution for use with an intranet. It includes email mailboxes, a fax viewer and sending function, contact lists, an appointment and task management function, a picture database, and a function for listening to voice messages. The extensive user management enables administrators to assign various permissions to each user and to exchange data e.g. contacts, appointments, or tasks. It also offers a function to import existing data.
OpenGroupware.org is a set of applications for contact, appointment, project, and content management. It is comparable to Exchange and SharePoint. It is accessible using Web interfaces or using local clients via WebDAV, GroupDAV, and CalDAV. Custom applications can be developed using the XML-RPC API. OpenGroupware.org runs on almost every GNU/Linux system.
j-XChange is a pure Java implementation of the entire Collaboration Data Objects (CDO 1.21) library for accessing Microsoft Exchange Server in a platform independent manner. This library will allow interoperability with MS Exchange from all non-Windows platforms that support Java. This library is powered by j-Interop.
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 POP and IMAP troubleshooter serves to diagnose and solve connection problems from client machines to email services. It reads the client configuration files (Outlook, Windows Mail, Thunderbird, etc.), checks the individual settings, and then attempts to create POP, IMAP, and SMTP connections using these settings. The troubleshooter is coded in C++ using the Qt environment. It can be used generically, or can be customized for the demands of a particular email service.
Xuheki is a fully featured email (IMAP) client for the Web. It looks and feels like an application rather than a Web site. It is fast, clean, and features no page reloads. It supports multiple users per installment, multiple IMAP servers per user, and multiple folders per IMAP server. It also supports text or HTML email, attachments, inline images, printing, and more. It has an "AJAX" interface that could compete with desktop-based mail user agents.