K-9 Mail

Name: K-9 Mail
Availability: InStock
Rating: 3.345599889755249 (99773 reviews)
Author: Mozilla Thunderbird

Mozilla Thunderbird

In-app purchases

99.8K reviews

USK: All ages

5M+

Downloads

USK: All ages

Users Interact

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About this app

K-9 Mail is an open source email client that works with basically every email provider.

Features

* supports multiple accounts
* Unified Inbox
* privacy-friendly (no tracking whatsoever, only connects to your email provider)
* automatic background synchronization or push notifications
* local and server-side search
* OpenPGP email encryption (PGP/MIME)

Install the app "OpenKeychain: Easy PGP" to encrypt/decrypt your emails using OpenPGP.

Support

If you're having trouble with K-9 Mail, ask for help in our support forum at https://forum.k9mail.app

Want to help?

K-9 Mail is now part of the Thunderbird family and remains a community developed project. If you're interested in helping to improve the app, please join us! You can find our bug tracker, source code, and wiki at https://github.com/thunderbird/thunderbird-android
We're always happy to welcome new developers, designers, documenters, translators, bug triagers and friends.

K-9 Mail is a 100% open source, privacy focused email client for Android

Updated on

Oct 6, 2026

Data safety

Safety starts with understanding how developers collect and share your data. Data privacy and security practices may vary based on your use, region, and age. The developer provided this information and may update it over time.

No data shared with third parties
Learn more about how developers declare sharing
No data collected
Learn more about how developers declare collection
Data is encrypted in transit
Data can’t be deleted

Ratings and reviews

94.5K reviews

Marco B

November 14, 2021

Failed redesign, now i can just use any other mail app. Setup for accounts is easier in other apps, since they detect settings by themselves. I used to choose K9 for monitoring several email accounts. It's a real hassle if you got a few accounts and don't want to use a unified inbox. So instead of just glimpsing on my private accounts and see if they got anything, i have to go through them all. Especially business mail accounts receive more mail, so you have to scroll down and down and down :(

71 people found this review helpful

yet_another_account yet_another_account

November 30, 2025

Still one of the best mail apps out there and open source! Today had to install it from scratch on a new phone. It took me a while to find again how to configure everything, particularly font sizes and hiding the push notification. in principle, all functionality is there, but documentation could be a bit clearer sometimes. but in the end, I prefer to have plenty of options over oversimplifying things, so I think it is good as it is.

15 people found this review helpful

Stefan Glandorf

July 28, 2021

I cannot recommend the update from v5.6 to v5.8. The new UI looks modern, but is no longer as functional. The view of multiple mailboxes has disappeared, there are fewer setting options, i cant find mail filters and a notification that bothers me is now permanently visible in the statusbar. It looks to me like the special features of k9 have disappeared and you can use Outlook just as well. K9 used to be very good, but I don't like the update at all.

34 people found this review helpful