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Horde Groupware vs Zimbra: catalog facts
Horde Groupware	Zimbra
Free Free and open source with no paid tier.	Paid Sold in several editions under Zimbra's license terms; see the edition comparison.
Web, Self-hosted	Web, Self-hosted
Full groupware suite beyond mail, including tasks, notes and time tracking CalDAV, CardDAV and ActiveSync sync	Mail, calendar and contacts in one web client Can be run on your own servers
Requires running and maintaining a PHP server Older codebase with a long history of security fixes to track	Aimed at organisations rather than individuals Running a mail server takes administration effort
Self-hosted	Self-hosted, Hosted service
Open source	Closed source
License: LGPL/GPL	License not stated
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 1, 2026

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