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Apache James vs Stalwart: catalog facts
Apache James	Stalwart
Free Free and open source from the Apache Software Foundation.	Free Free and open source, self-hosted.
Self-hosted	Linux, Self-hosted
Supports modern JMAP alongside SMTP, IMAP and POP3 Mailet container for custom mail processing	Modern JMAP support alongside traditional IMAP and SMTP protocols Rust implementation aims for security and performance
Requires a Java runtime and some server administration knowledge Distributed setups depend on extra services such as Cassandra	Requires self-hosting and server administration knowledge Newer project with a smaller ecosystem than long-established mail 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 September 22, 2026

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