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, and contacts
Forums, mailing lists, and instant messaging
Wiki, blog, and RSS aggregation
Multi‑domain support with a powerful web interface
Written in C - lean, fast, and memory safe
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.
