Citadel
The facts below are what the maker publishes about Citadel, checked and dated. Our editors have not written about it yet.
Plans and prices
From Citadel's own pricing page, checked 30 Sep 2026.
| Plan | Price | What it gives you |
|---|---|---|
| Citadel software | Free | 100% open source · GNU General Public License · self-hosted or cloud deployment |
The facts
Each one read from Citadel's own pages, with the date it was checked.
What it does
- Architecture
- Citadel uses a rooms-based architecture for organizing collaboration features.checked 30 Sep 2026
- Authentication
- Citadel can authenticate users through its own database, host-system accounts, or LDAP including Microsoft Active Directory schemas.checked 30 Sep 2026
- Calendar integration
- Calendar and address-book functions are available to PIM clients supporting Webcal or GroupDAV.checked 30 Sep 2026
- Core features
- The system includes email, calendars, contacts, forums, mailing lists, instant messaging, wikis, blogs, and RSS aggregation.checked 30 Sep 2026
- Deployment
- Citadel can run in Docker, through a Linux build script, from source, or via a hosting provider.checked 30 Sep 2026
- Email clients
- Citadel provides built-in SMTP, POP, and IMAP services and works with standards-compliant clients such as Thunderbird and Outlook.checked 30 Sep 2026
- Encryption
- Citadel provides TLS encryption for ESMTP, IMAP, POP3, and the Citadel client protocol.checked 30 Sep 2026
- History
- Citadel began in December 1981 as a dial-up BBS package written by Jeff Prothero for 8-bit CP/M systems.checked 30 Sep 2026
- Message journaling
- Citadel journaling records processed messages but is not itself an archival service, so the project recommends pairing it with a third-party archival product or service.checked 30 Sep 2026
- Purpose
- Citadel is an email, collaboration, groupware, and content-management system.checked 30 Sep 2026
- Support
- Support is provided through an active user and developer community, an online knowledge base, a support forum, and a mailing list.checked 30 Sep 2026
- System requirements
- Manual installation requires a modern Unix operating system, root access, Berkeley DB 5 or newer, and libical 3 or newer.checked 30 Sep 2026
- Web access
- WebCit provides full access to Citadel through a web browser.checked 30 Sep 2026
Where it runs
- Docker platforms
- The Docker image offers AMD64, i386, ARMv7, and ARM64 builds.checked 30 Sep 2026
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