K-9 Mail Android
K-9 Mail is #165 in Communication Free on Google Play in Germany and charting in 2 of 15 countries we track.
Updated 27 Sep 2026 · rankings refresh through the day
DeveloperMozilla Thunderbird
CategoryCommunication
PriceFree
Released–
Installs5M+
Rating★ 3.3 (100k)
Updated
Content ratingEveryone
Rating
3.3 ★
100k ratings
Measured
Best rank now
#165
Communication FreeMeasured
K-9 Mail on Google Play
App details
App ID
com.fsck.k9
Publisher
Mozilla Thunderbird
Content rating
Everyone
K-9 Mail downloads
Worldwide, per day, and installs to date. The band is open; the exact number is free with an account.
How this is calculated
Google Play shows an exact lifetime install count; downloads per day are its daily change (measured). When Play hasn't refreshed the count, they come from new ratings and Top Free chart positions. Confidence is the chance the real number is within half to double ours.
Active users
All platforms, worldwide. Free with an account.
Stickiness (DAU / MAU)
how many monthly users open it on a given day
How this is calculated
Monthly users come from lifetime installs across every store, fitted on monthly active user figures companies publish; daily users = monthly × the typical daily/monthly ratio for the category. Confidence is the chance the real number is within half to double ours.
In-app revenue
Worldwide, what users spend in K-9 Mail before Apple and Google take their fee.
How this is calculated
Not on any Top Grossing chart: monthly active users × spend per user for its category, measured on the charted apps nearest the bottom of the charts.
Business model: In-app purchase-led
How K-9 Mail makes money: subscriptions, one-off purchases and ads.
In-app purchases
One-off purchases
/mo
of revenue
Where it ranks on Google Play
Every top 200 chart it appears in across 15 countries.
| Country | Charts | Rank |
|---|---|---|
| Germany | CommunicationFree | #165 |
 Italy | CommunicationFree | #129 |
Apps near K-9 Mail on the chart
Communication Free, around #165.
Ratings
Google Play, worldwide.
Rating
3.3 ★
100k ratings
Measured
Ratings
100k
Measured
Written reviews
11k
Measured
About K-9 Mail
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.
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.
What's new in 23.1
K-9 Mail version 23.1
Fixed:
- Attachment filenames with non-ASCII characters were incorrectly decoded and saved
Fixed:
- Attachment filenames with non-ASCII characters were incorrectly decoded and saved