Compare software

K-9 Mail vs Slow Mail: catalog facts
K-9 Mail	Slow Mail
Free Free and open source.	Free Free and open source under the MIT licence.
Android	Android
Open source with a long track record on Android Now the foundation for Thunderbird's official mobile app	No emails or message lists stored on the device Works with any IMAP and SMTP provider
Android only, no iOS version Interface is more utilitarian than modern polished mail apps	Needs an active internet connection to read mail Slower than clients with a local cache
Downloadable app	Downloadable app
Open source	Open source
License: Apache-2.0	License: MIT
Not stated if an account is needed	Not stated if an account is needed
Not stated if it works offline	Needs internet
Official website Full listing and sources Checked September 22, 2026	Official website Full listing and sources Checked October 2, 2026

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