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grommunio vs Zimbra: catalog facts
grommunio	Zimbra
Freemium Open source, with paid plans listed on the pricing page.	Paid Sold in several editions under Zimbra's license terms; see the edition comparison.
Linux, Web, Self-hosted	Web, Self-hosted
Native MAPI, EWS and EAS support for Outlook and mobile clients Mail, calendars, chat, video and files on one platform	Mail, calendar and contacts in one web client Can be run on your own servers
Running a groupware server requires administration skills Some features may depend on paid plans	Aimed at organisations rather than individuals Running a mail server takes administration effort
Self-hosted, Hosted service	Self-hosted, Hosted service
Open source	Closed source
License not stated	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 October 1, 2026	Official website Full listing and sources Checked October 1, 2026

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