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Last updated on: 2025-06-11
Android Apps > Communication > K-9 Mail
K-9 Mail icon

K-9 Mail

10.0
Mozilla Thunderbird
3.35
94,611 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
Interested in open source? Check out the top awesome open source projects! Top open source projects

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 14 thousand times.
It's highly ranked.
It's rated 3.35 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 14 thousand
Rating 3.35 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

Secure Emails Inbox Encryption Access Encrypted Security Features Messages Private Free Send Cloud Mailbox Contacts Privacy Address Create Pgp Key Notifications Calendar Proton Account Full Easy Online Data Files Experience Attachments People Manage Mailfence Imap Exchange Receive Set Storage Protect Recent View

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Google Play Rating history and histogram

41K
11K
9K
9.4K
25K

Downloads over time

K-9 Mail has been downloaded 9.4 million times. Over the past 30 days, it averaged 480 downloads per day.

Changelog of K-9 Mail

Show changelog

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

★★★★★ Synced smoothly with all of my email accounts and accessed every folder for each of them which makes properly organizing saved emails from one app possible. Decently small app size. Well done! The ability to create new folders would be useful. Doesn't work with slow internet.
★★★★★ Failed. Got on adding an email address from Google: This app is blocked This app tried to access sensitive info in your Google Account. To keep your account safe, Google blocked this access. Updated. Zoho email address does add successfully. Microsoft email address DOES add successfully.
★★★★★ 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.
★★★★★ 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!
★★☆☆☆ I can't log in my gmail account as it says Google blocked login for security
★★☆☆☆ 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.
★★☆☆☆ 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

Google Play Rankings for K-9 Mail

Top rankings

Rank Country Category List
78 Germany Communication Top Grossing
87 Japan Communication Top Grossing
144 Austria Communication Top Free
156 Switzerland Communication Top Free
183 Slovakia Communication Top Free
61 Austria Communication Top Grossing
151 Switzerland Communication Top Grossing
198 United Kingdom Communication Top Grossing
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Ranking history in Austria

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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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