Freedom251 › Mail Server Software
Citadel
Plans
| Plan | Billed and limits | Price |
|---|---|---|
| Citadel software | 100% open source · GNU General Public License · self-hosted or cloud deployment | Free |
As citadel.org lists them, read 30 Sept 2026. The maker's own page has the final word.
Facts from Citadel's own pages
- Architecture
- Citadel uses a rooms-based architecture for organizing collaboration features. · citadel.org, 30 Sept 2026
- Authentication
- Citadel can authenticate users through its own database, host-system accounts, or LDAP including Microsoft Active Directory schemas. · citadel.org, 30 Sept 2026
- Calendar integration
- Calendar and address-book functions are available to PIM clients supporting Webcal or GroupDAV. · citadel.org, 30 Sept 2026
- Core features
- The system includes email, calendars, contacts, forums, mailing lists, instant messaging, wikis, blogs, and RSS aggregation. · citadel.org, 30 Sept 2026
- Deployment
- Citadel can run in Docker, through a Linux build script, from source, or via a hosting provider. · citadel.org, 30 Sept 2026
- Docker platforms
- The Docker image offers AMD64, i386, ARMv7, and ARM64 builds. · citadel.org, 30 Sept 2026
- Email clients
- Citadel provides built-in SMTP, POP, and IMAP services and works with standards-compliant clients such as Thunderbird and Outlook. · citadel.org, 30 Sept 2026
- Encryption
- Citadel provides TLS encryption for ESMTP, IMAP, POP3, and the Citadel client protocol. · citadel.org, 30 Sept 2026
- History
- Citadel began in December 1981 as a dial-up BBS package written by Jeff Prothero for 8-bit CP/M systems. · citadel.org, 30 Sept 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. · citadel.org, 30 Sept 2026
- Purpose
- Citadel is an email, collaboration, groupware, and content-management system. · citadel.org, 30 Sept 2026
- Support
- Support is provided through an active user and developer community, an online knowledge base, a support forum, and a mailing list. · citadel.org, 30 Sept 2026
- System requirements
- Manual installation requires a modern Unix operating system, root access, Berkeley DB 5 or newer, and libical 3 or newer. · citadel.org, 30 Sept 2026
- Web access
- WebCit provides full access to Citadel through a web browser. · citadel.org, 30 Sept 2026
Where Citadel stands on Freedom251
- Mail Server Software#3 of 34
- Mailing List Management Software#3 of 21