K-9 Mail

K-9 Mail

Mozilla Thunderbird·3.0 ★·FREE
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Screenshots

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Description

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.

Developer

Mozilla Thunderbird

Developer ID: 8696262544613553264

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Ratings & Reviews

3.0

99,773 ratings

5,000,000+ downloads

5★
34%
4★
13%
3★
10%
2★
10%
1★
33%

Recent Reviews

M

v23.0

UPDATE: I'll take your word for it but that's a heck of a coincidence. Only thing that changed. Plus I'm assuming, hoping, you're not like those other greedy, data harvesting jerks. Mail still never syncs in real time though. OLD: *The only thing that isn't apparent to me is if your email is secured like Gmail and others, uses TLS encryption etc, or is susceptible to MiTM attacks and such. 👍

Developer Response

This was likely not the cause of K-9 since it is just an email client and not an email service. There is built in security in the app, but you are also welcome to send and receive encrypted emails using the OpenPGP standard when paired with something like the free and open source OpenKeychain app in order to make sure nothing is being intercepted.

Sep 21, 2026

Sep 23, 2026

A K

v23.0

So how will outlook know that i want to report the wrongly flagged email as not junk? I just move it to inbox? Does that suffice?

Developer Response

Hello A K: Yes, please move the wrong flagged email to the inbox as well as flag it as junk.

Sep 23, 2026

Sep 22, 2026

gkatachi

v23.0

Amazing app, I've been a user for years. Small bug that caused me a big headache recently: when pressing save all attachments on received mail, the files downloaded are replicated despite being saved under different (correct) names in my directory. I've noticed its the attachment at the bottom of the list that being repeated usually.

Sep 14, 2026

Jane Doe

v23.0

It worked OK for awhile, but can not handle attachments now, and there are no formatting options for type.

Developer Response

As requested previously: If you can Jane, please do create a support question and update with a link to the support question: https://support.mozilla.org/questions/new/thunderbird-android/form We'll help further there.

Sep 15, 2026

Sep 14, 2026

Kanzan Cherry

v5.600

It's been 5 years since the redesign ruined K-9 Mail. Let me know when you go back to being a good email client. I'm very disappointed in you.

Developer Response

We're sorry for any frustration with the new design of the K-9 Mail app. One of our major design and development goals is to make the app easier and more intuitive to use. Thanks for your patience while we get this right, and you can also give feedback at connect.mozilla.org!

Sep 14, 2026

Sep 14, 2026

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