One of the most important features for many people is the ease of use and installation.  Citadel tries to eliminate all of the hassel in setting up a Mail server with groupware.  This example uses Postfix for the install.

The website has a lot of valuable information and there is adequate documentation for the set up and management of the mail server.

• Email, calendaring, address books, bulletin boards, instant messaging, and more … all in one tightly integrated server package.

• High-performance, multiprotocol, multithreaded server engine

• Web browser, telnet/SSH, local client software accessible

• Standards-compliant e-mail built in: IMAP, POP3, ESMTP

• Group calendaring and scheduling (GroupDAV and Kolab-1 compatible)

• Built-in listserv (mailing list server)

• Integrated server-side mail sorting and filtering. Users can choose between an easy-to-use web based rules editor, or the power of writing complex scripts using the industry standard Sieve language.

• Support for push e-mail and mobile devices

• Database-driven, single-instance message store

• Built-in full text index for fast searching

• Authenticated SMTP for remote email submission

• Multiple domain support

• Built-in integration with perimiter email filtering technologies such as Realtime Blackhole Lists (RBL’s) and SpamAssassin

• Server-to-server replication. Users in any number of domains can be spread out across any number of Citadel servers, allowing you to put data where you need it, and enabling infinite horizontal scalability.

• Web-based access to email, calendars, and everything else through a powerful AJAX-style front end

• Very strong support for “public folders” and message forums.

• Built-in instant messenger service

• SSL/TLS encryption for all protocols

• LDAP integration capabilities. Citadel can populate your existing directory server, or it can configure a standalone directory server if you don’t already have one.

• Citadel is true open source software.