Kolab

Kolab is a free and open source groupware suite. It consists of the Kolab server and a wide variety of Kolab clients, including KDE PIM-Suite Kontact, Roundcube web frontend, Mozilla Thunderbird and Mozilla Lightning with SyncKolab extension and Microsoft Outlook with proprietary Kolab-Connector PlugIns.
Basic Concepts.
Kolab uses IMAP as an underlying protocol for email, contact, and calendar entries. These entries are saved in IMAP folders in Kolab XML format, and the IMAP server controls storage and access rights. Configuration and maintenance of Kolab is done by LDAP.
Kolab Clients and the Kolab server use well established protocols and formats for their work (i.e. IMAP as mentioned above, vCard, iCal, XML and LDAP). This allows the Kolab Format specification framework, or even portions of it, to be utilized as an open set of specifications for groupware clients and servers to communicate with each other. Third party implementations began almost immediately; for example, the Citadel groupware server began supporting version 1 of the Kolab Format specification in March 2004.
The concepts on which Kolab relies are laid out in the "Kolab Format Specification" and "Architecture Paper" for Kolab 2, and for Kolab 1 in the "Kroupware Contract", "Architecture Paper" and "Technical Description".
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