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Meet the Citadel System.
Easy to install. Easy to use. 100% open source. No compromises.

Email, collaboration, groupware, and content management -
up and running in minutes, on your own hardware or in the cloud.

Powerful and flexible

Citadel is easy, versatile, and powerful, thanks to its exclusive "rooms" based architecture. No other platform seamlessly combines so many different features using this familiar and consistent metaphor.

Packed with features

  • email
  • calendar/scheduling
  • address books
  • bulletin boards (forums)
  • mailing list server
  • instant messaging
  • wiki and blog engines
  • multiple domain support
  • a powerful web interface
  • rss aggregation

True open source

Citadel is 100% open source software using the GNU General Public License. It's not a crippled, cut-down version of some expensive "enterprise" edition. The software you download here is the very best available, and it's all free software.

Best of all, the Citadel project pledges never to let entryists ruin its code of conduct. We know that social justice warriors destroy everything they touch.

There are no social media links here. Enjoy a friendly Citadel community instead. Or go outside.