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Zimbra vs WildDuck: catalog facts
Zimbra	WildDuck
Paid Sold in several editions under Zimbra's license terms; see the edition comparison.	Free Free open-source software that you host yourself.
Web, Self-hosted	Linux, Self-hosted
Mail, calendar and contacts in one web client Can be run on your own servers	Horizontal scaling with no single point of failure Full IMAP4rev1 support with many extensions
Aimed at organisations rather than individuals Running a mail server takes administration effort	Needs MongoDB, Redis and separate SMTP components Aimed at large deployments rather than small personal servers
Self-hosted, Hosted service	Self-hosted
Closed source	Open 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.