Citadel vs Kolab Groupware
A side-by-side comparison of two self-hosted groupware options — licensing, setup difficulty, resource needs, and what each one replaces.
Not the right match-up?
Citadel
All-in-one groupware, mail and collaboration server
VS
Kolab Groupware
Open-source groupware server with mail and calendaring
| Feature | Citadel | Kolab Groupware |
|---|---|---|
| Category | Groupware | Groupware |
| License | GPL-3.0 | AGPL-3.0 |
| Language | C | PHP |
| Setup difficulty | Medium | Hard |
| Min. RAM | 512 MB | 2,048 MB |
| Deployment | bare-metal, source | bare-metal, docker |
| GitHub stars | ★ 100 | ★ 200 |
| First released | 1987 | 2002 |
| Replaces | Microsoft Exchange, Microsoft 365 | Microsoft Exchange, Zimbra |
Why pick each one
Choose Kolab Groupware if…
- Built on proven components
- Strong standards support
Frequently asked questions
Is Citadel or Kolab Groupware better?
Neither is universally better. Kolab Groupware has the larger community, while Citadel is simpler to set up (medium difficulty). Choose based on the comparison table above and your own setup.
Are Citadel and Kolab Groupware free and open-source?
Yes. Citadel is licensed under GPL-3.0 and Kolab Groupware under AGPL-3.0. Both can be self-hosted at no software cost.
Can I run Citadel and Kolab Groupware with Docker?
Citadel: check the project docs for container support. Kolab Groupware: yes.