Citadel vs SOGo
A side-by-side comparison of two self-hosted groupware options — licensing, setup difficulty, resource needs, and what each one replaces.
SOGo
Scalable groupware server with webmail, calendar and contacts
| Feature | Citadel | SOGo |
|---|---|---|
| Deploy effort | Read-the-docs project | Under-an-hour setup |
| Category | Groupware | Groupware |
| License | GPL-3.0 | GPL-2.0 |
| Language | C | Objective-C |
| Setup difficulty | Medium | Hard |
| Min. RAM | 512 MB | 1,024 MB |
| Deployment | bare-metal, source | docker, bare-metal |
| GitHub stars | ★ 100 | ★ 2,165 |
| First released | 1987 | 2009 |
| Replaces | Microsoft Exchange, Microsoft 365 | Microsoft Exchange, Microsoft 365 |
What are Citadel and SOGo?
Citadel
Citadel is a mature, all-in-one collaboration suite that integrates email, calendaring, address books, instant messaging, and bulletin boards. It is designed for easy installation and minimal maintenance.
- Integrated mail and calendar
- Built-in groupware web client
- Instant messaging and forums
- Easy installer
SOGo
SOGo is a fully featured, scalable groupware server offering shared calendars, address books, and webmail. It is fully compatible with Microsoft Outlook via ActiveSync and with CalDAV/CardDAV clients.
- CalDAV and CardDAV support
- Microsoft ActiveSync compatibility
- Shared calendars and contacts
- Integrated AJAX webmail
Citadel vs SOGo: key differences
Citadel is written in C, while SOGo is built with Objective-C. Licensing differs — GPL-3.0 for Citadel versus GPL-2.0 for SOGo. Citadel is the lighter option, starting around 512 MB of RAM against 1,024 MB for SOGo. Citadel is the more established project (first released 1987), while SOGo arrived in 2009. SOGo has the considerably larger community, at 2,165 GitHub stars versus 100. SOGo lists first-class Docker deployment; Citadel does not.
Why pick each one
Choose Citadel if…
- Single-package setup
- Low resource needs
Watch out for
- Niche project
- Old-fashioned UI
Choose SOGo if…
- Strong Outlook compatibility
- Scales to many users
Watch out for
- Complex initial setup
- Requires separate mail server
Frequently asked questions
Is Citadel or SOGo better?
Neither is universally better. SOGo 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 SOGo free and open-source?
Yes. Citadel is licensed under GPL-3.0 and SOGo under GPL-2.0. Both can be self-hosted at no software cost.
Can I run Citadel and SOGo with Docker?
Citadel: check the project docs for container support. SOGo: yes.
Which is lighter on resources, Citadel or SOGo?
Citadel has the smaller minimum footprint at 512 MB of RAM, compared to about 1,024 MB for SOGo. Real-world usage depends on library size, user count, and enabled features.