Citadel / UX is a free groupware with roots in the BBS scene. It provides functions for email, contacts, calendar and tasks. Citadel / UX is developed from an open developer community since 1994 under the GNU General Public License.

Overview of functions

  • Mail server SMTP MTA
  • IMAP server
  • Sieve -based mail filtering
  • POP3 server
  • Discussion Forums
  • Calendar
  • Contacts
  • Tasks
  • Webmail via webcit
  • Real-time chat in both the web interface or via XMPP and on the command line
  • Short messages to other users in the system ( Instant Messaging)
  • GroupDAV interface for calendar / contacts / tasks with fat clients
  • C programming
  • OpenSSL encryption for all protocols


Citadel has evolved from a system available on Unix platforms Bulletin Board. The original implementation dates back from 1987, running on an Altos 586 The lead programmer of Citadel / UX previously used Citadel and Citadel cpm -86 and decided to start a Unix port. The original name was Unix Rooms, but was later changed to Citadel / UX. In 1914- area code of the United States, dedicated to freedom of expression, provided the " Uncensored! BBS ' in the Citadel project home.