Compare software

SOGo vs Citadel: catalog facts
SOGo	Citadel
Free Free and open source; paid premium support is offered separately.	Free Free and open source under the GNU GPL, with no paid edition.
Web, Self-hosted	Web, Self-hosted
Webmail, calendars and contacts in one self-hosted server CalDAV, CardDAV and ActiveSync support for native and mobile clients	Mail, calendar, contacts, forums, wiki and chat in one server Consistent rooms-based structure across features
Needs existing mail and directory servers to integrate with Outlook support depends on a separate CalDAV synchronizer	The rooms metaphor differs from conventional mail servers Requires running and maintaining your own server
Self-hosted	Self-hosted
Open source	Open source
License: GPL-2.0-or-later / LGPL-2.0-or-later	License: GPL
Not stated if an account is needed	Not stated if an account is needed
Not stated if it works offline	Not stated if it works offline
Official website Full listing and sources Checked September 23, 2026	Official website Full listing and sources Checked October 2, 2026

Catalog facts only. Anything “not stated” is unconfirmed. Check full listings for details.