Exim vs Citadel
A side-by-side comparison of two self-hosted apps from related categories — licensing, setup difficulty, resource needs, and what each one replaces.
Not the right match-up?
Exim
Flexible and widely deployed mail transfer agent
VS
Citadel
All-in-one groupware, mail and collaboration server
| Feature | Exim | Citadel |
|---|---|---|
| Category | Mail Servers | Groupware |
| License | GPL-2.0 | GPL-3.0 |
| Language | C | C |
| Setup difficulty | Hard | Medium |
| Min. RAM | 64 MB | 512 MB |
| Deployment | bare-metal, source | bare-metal, source |
| GitHub stars | ★ 786 | ★ 100 |
| First released | 1995 | 1987 |
| Replaces | Microsoft Exchange | Microsoft Exchange, Microsoft 365 |
Why pick each one
Frequently asked questions
Is Exim or Citadel better?
Neither is universally better. Exim 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 Exim and Citadel free and open-source?
Yes. Exim is licensed under GPL-2.0 and Citadel under GPL-3.0. Both can be self-hosted at no software cost.
Can I run Exim and Citadel with Docker?
Exim: check the project docs for container support. Citadel: check the project docs for container support.