Projects / Citadel


Citadel is an advanced messaging and collaboration system for groupware and BBS applications. Users can connect to Citadel using any telnet, WWW, or client software. Among the features supported are public and private message bases (rooms), electronic mail, real-time chat, paging, shared calendaring, address books, mailing lists, and more. Unlike other collaboration servers, Citadel provides its own data stores and is therefore extremely easy to install; you don't have to "bring your own" email and database because they're built in. The server is multithreaded and scalable. In addition, SMTP, IMAP, and POP3 servers are built-in for easy connection to Internet mail. Citadel is both robust and mature; it has been in production since 1987.

Operating Systems

Recent releases

  •  16 Aug 2010 16:04

    Release Notes: New features include a greatly improved XMPP (Jabber) service for better compatibility with more instant messenger clients, a completely new bulletin board (forum) view that is greatly improved in both performance and features, a brand new multiuser chat facility redesigned for better access through a Web browser, and many bugfixes and performance enhancements.

    •  23 Feb 2010 15:06

      Release Notes: The following issues have been fixed: line-buffered I/O was handled incorrectly; when configuring a brand new Citadel installation for LDAP authentication, the LDAP configuration would be erased on the first server run and would need to be re-entered; issues with LDAP authentication on 64-bit systems; deleting the last unread message in a room would sometimes fail to mark the room as not containing new messages; a memory leak was associated with binary downloads; a small bug was in the Wiki room mode on 64-bit systems; a buffer size issue was in the text mode client.

      •  13 Apr 2009 16:35

        Release Notes: Recurring events are now supported across the entire calendar system, as well as all-day events which span multiple days. The WebCit framework is now templatized. The mailbox summary view is now faster and more versatile. Support for virus scanning with ClamAV was integrated. Inline images are supported in message views. Interoperability with vCards generated by third-party address book software was improved. Fonts in WebCit are now relative sized, making the whole site look better on screens of all sizes. Performance improvements, user interface enhancements, and bugfixes were made.

        •  23 Sep 2008 17:39

          Release Notes: When running mailing lists, the List-ID field is parsed and generated. Improved handling of the refcount_adjustments.dat file to prevent a rare condition where the file can't be renamed and therefore cannot be processed. The display of incoming instant messages through an IMAP client has been removed, because XMPP is now supported, so it would be redundant for most users.

          •  10 Mar 2008 17:40

            Release Notes: This version adds an XMPP (Jabber) service. It also adds more security and granularity to the options provided by Citadel-hosted mailing lists.

            Recent comments

            28 Dec 2006 08:07 mikecrowe

            Move over postfix....
            When hosting my personal and church site, I needed a flexible, easily administered solution. After implementing (yes, successfully) a postfix virtual email system, I recently found Citadel (actually, I had crashed my server, and was seriously dreading re-implementing postfix).

            Installation? EasyInstall, and boy is it

            Configuration? Browser based. Here's what it took:

            1) Receiving emails for,, ...

            2) Enter the users for each domain

            3) Tell it I had spamassin running on the machine.

            I was floored. It was receiving all my emails. Amazing.

            Then, I needed a mailing-list type functionality. Create a "room" called Finances. Subscribe to that room for the people who need updates, and suddenly all emails to are now distributed as a mailing list. Wow.

            An excellent product, excellent development community, very good web client/email tool. What more could you ask for?

            Give it a shot today...

            13 Sep 2005 09:26 ajc

            14 Feb 1999 22:12 crackmonkey

            Cynbe ru Taren's original comments on Citadel

            Citadel is a room-structured message system. The fundamental
            design goal is to provide a congenial forum conducive to interesting
            discussions. The software is intended to be as unobtrusive, unintrusive
            and unconstraining as possible. In software as elsewhere, good engineering
            is whatever gets the job done without calling attention to itself.

            The fundamental design metaphor is that of a building consisting of
            a series of independent rooms, each of which hosts a discussion devoted
            to a particular topic. Messages are stored and retrieved in chronological
            order within each room. Messages are formatted to the caller's screen width.

            Callers may travel freely between the rooms,
            reading old messages and posting new ones. New rooms may be created
            at will, and old ones are deleted when they empty of messages.

            People familiar with other electronic message systems may wish
            to compare Citadel rooms with EIES conferences, ArpaNet mailing
            lists, individual "linear" BB systems or whatever; the parallels
            are not exact but the functions are similar.

            The fundamental Goto, Read and Enter commands have been streamlined
            as much as possible. The message display format has a minimum of
            unnecessary noise: the topic is implicit in the message's location
            within a room, no explicit TO field is present, no message ID # is
            printed, no redundant "END OF MESSAGE" blurbs etc. The most common Goto,
            Read and Enter commands are all single-key. Citadel automatically
            skips rooms which have no new messages, and old messages in the
            current room. (Less concise commands are of course available to
            override this.)


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