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Last updated on: 2025-07-11
Android Apps > Communication > K-9 Mail
K-9 Mail icon

K-9 Mail

10.0
Mozilla Thunderbird
3.34
94,658 reviews
5,000,000+
Downloads
Free

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

K-9 Mail Screenshot
K-9 Mail Screenshot
K-9 Mail Screenshot
K-9 Mail Screenshot
K-9 Mail Screenshot
K-9 Mail Screenshot
K-9 Mail Screenshot
K-9 Mail Screenshot
Google Play

About K-9 Mail

K-9 Mail is a communication app developed by Mozilla Thunderbird. The APK has been available since before 2010. In the last 30 days, the app was downloaded about 15 thousand times.
It's highly ranked.
It's rated 3.34 out of 5 stars, based on 95 thousand ratings. The last update of the app was on May 8, 2025. K-9 Mail has a content rating "Everyone".
K-9 Mail has an APK download size of 10.78 MB and the latest version available is 10.0. Designed for Android version 5.0+. K-9 Mail is FREE to download.
Description
K-9 Mail is an open source email client that works with basically every email provider.
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More data about K-9 Mail

Price Free to download
Total downloads 9.4 million
Recent downloads 15 thousand
Rating 3.34 based on 95 thousand ratings
Ranking Highly ranked
Version 10.0
APK size 10.8 MB
Number of libraries 30
Designed for Android 5.0+
Suitable for Everyone
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K-9 Mail compared with similar apps

Common keywords of similar apps

Source Thunderbird Update Open Provider Openpgp Forum Bug Mail Email App Client Accounts Support Https

Keywords missing from this app

Emails Secure Inbox Encryption Access Encrypted Security Mailbox Features Free Messages Send Private Cloud Easy Privacy Create Pgp Address Protect Proton Key Receive Contacts Online Easily Notifications Calendar People Set Account Data Mailfence Experience Manage Multiple Attachments Recent Addresses Information Files Screen

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Google Play Rating history and histogram

41K
10K
9.5K
9.2K
25K

Downloads over time

K-9 Mail has been downloaded 9.4 million times. Over the past 30 days, it averaged 500 downloads per day.

Changelog of K-9 Mail

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Developer information for Mozilla Thunderbird

Mozilla Thunderbird

thunderbird-android-feedback@thunderbird.net

Website

N/A

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Share and embed K-9 Mail

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Comments on K-9 Mail for Android

★★★★★ Best replacement for stock telco/android email apps that start to have problems after a year or become bloated. Light, fast, dark mode and options under the hood (synching options + more). It works best for my personal email needs. You can set it to use "push" so you get mail quickly or use "fetch" on a schedule. [GMail is good as r many others, but I want an app for my personal stuff not accessible by corporations. Open Source!
★★★★★ It's a pity it isn't possible to create new e-mail folders, only move messages to existing ones. Apart from that, that's a great mobile e-mail client.
★★★★★ A Hidden Gem for PGP-Encrypted Email! K-9 Mail is an outstanding open-source email app, and its seamless integration with OpenKeychain makes it a must-have for anyone looking to send encrypted emails effortlessly. If you're searching for an easy way to create and use PGP encryption, this app makes it incredibly simple—just pull in your key from OpenKeychain and start sending secure emails right away. No complicated setup, no headaches—just secure, private communication made easy.
★★☆☆☆ Hi, Every time I'm trying to send an email with or without an attached document, it won't be sent but instead end up in the outbox. What should I do? Because I've used another app and that one gives me the same result but tells me that my email has been classified as spam by my email provider, so I believe this has something to do with my emails considered to be spams by K9 mail though they're not because when I send emails through my regular email client it works just fine. Thanks
★★☆☆☆ Personally, I have a problem with widgets that don't have a dark mode option. In general, I agree with others, the email homepage should have some kind of toggle to switch accounts (like gmail and outlook).
★★☆☆☆ I wanted to like this app, but I don't. It does not sync emails despite my global settings. Have to constantly refresh manually to download messages. The layout is okay, I like the unified inbox, but that's about it. I have to constantly tell it to show remote images and/or download complete message manually, as I have not been able to locate a global setting for this. It's a pain. Going back to Mozilla Thunderbird. UPDATE: Thx for Dev response. Did all that prior to review. Still doesn't work.

Google Play Rankings for K-9 Mail

Top rankings

Rank Country Category List
199 Germany Communication Top Free
106 Austria Communication Top Free
91 Germany Communication Top Grossing
162 Switzerland Communication Top Free
199 Sweden Communication Top Free
134 Japan Communication Top Grossing
78 Austria Communication Top Grossing
78 Switzerland Communication Top Grossing
161 Canada Communication Top Grossing
197 United Kingdom Communication Top Grossing
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Ranking history in Germany

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Technologies used by K-9 Mail

K-9 Mail is requesting 16 permissions and is using 33 libraries.
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