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

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