Compare software

K-9 Mail vs Simple Email: catalog facts
K-9 Mail	Simple Email
Free Free and open source.	Free Free software under the GPL-3.0 license.
Android	Android
Open source with a long track record on Android Now the foundation for Thunderbird's official mobile app	Unified inbox for multiple accounts Offline storage and operations
Android only, no iOS version Interface is more utilitarian than modern polished mail apps	Android only
Downloadable app	Downloadable app
Open source	Open source
License: Apache-2.0	License: GPL-3.0-only
Not stated if an account is needed	Not stated if an account is needed
Not stated if it works offline	Works offline
Official website Full listing and sources Checked September 22, 2026	Official website Full listing and sources Checked October 8, 2026

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