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Apache James vs WildDuck: catalog facts
Apache James	WildDuck
Free Free and open source from the Apache Software Foundation.	Free Free open-source software that you host yourself.
Self-hosted	Linux, Self-hosted
Supports modern JMAP alongside SMTP, IMAP and POP3 Mailet container for custom mail processing	Horizontal scaling with no single point of failure Full IMAP4rev1 support with many extensions
Requires a Java runtime and some server administration knowledge Distributed setups depend on extra services such as Cassandra	Needs MongoDB, Redis and separate SMTP components Aimed at large deployments rather than small personal servers
Self-hosted	Self-hosted
Open source	Open source
License: Apache-2.0	License not stated
No account 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 2, 2026	Official website Full listing and sources Checked October 1, 2026

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