Compare software

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

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