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K-9 Mail vs Edison Mail: catalog facts
K-9 Mail	Edison Mail
Free Free and open source.	Free Offered as a download; the homepage does not list prices.
Android	macOS, Android, iOS
Open source with a long track record on Android Now the foundation for Thunderbird's official mobile app	Unified inbox across several email accounts Available on phones and the Mac
Android only, no iOS version Interface is more utilitarian than modern polished mail apps	No Windows or Linux version Closed source
Downloadable app	Downloadable app
Open source	Closed source
License: Apache-2.0	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 22, 2026	Official website Full listing and sources Checked September 23, 2026

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