K-9 Mail review (2026): is it any good?
Open source email client for Android, now moving to Thunderbird
K-9 Mail report card
Good · out of 4.0 · graded Nov 13, 2026
Best for an open-source Android email client
K-9 Mail is a free, open-source email app for Android with push IMAP, a unified inbox, several identities and GPG signing. The project's own site now says Thunderbird for Android is the future of K-9 Mail. It is Android only and only a client, so it brings no mailbox of its own.
Who K-9 Mail is for
- Fits if you read several mailboxes on one Android phone
- Works for people who want GPG and open-source code
Who K-9 Mail is not for
- Not for you if you use iPhone or a computer, as it is Android only
- Watch out: the site's banner says Thunderbird for Android is the future of K-9 Mail
- Skip it if you need a new address, since it is a client for existing mailboxes
- Tight if you want setup done for you, as you add your own account details
Why K-9 Mail gets a 2.8
Five grades, each with its reason. The GPA is their average: an A is 4 points, an F is none.
- AValue for moneyFree to download under the Apache 2.0 licence, with no paid plans, and a donate link.
- AFree plan and trialThe full app is free from Google Play, F-Droid, GitHub or Amazon.
- BFeaturesPush IMAP, GPG and PGP/MIME, a unified inbox, identities and message tools. The listing shows no gap in the core job of a mail client, though it provides no address of its own.
- CEase of useNo store rating on record. You add your accounts and server settings yourself.
- DPlatforms and integrationsAndroid only: no iPhone, desktop or web version is listed.
What these grades rest on. Graded from this listing, whose facts were read from K-9 Mail's own pages on 13 November 2026. Not based on using the product, and shorter than our full reviews. How we review and grade.
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<a href="https://toolgpa.com/tools/k-9-mail#review"><img src="https://toolgpa.com/badge/k-9-mail.svg" alt="K-9 Mail: 2.8 GPA on ToolGPA" width="196" height="56"></a>Where K-9 Mail stands among email apps
K-9 Mail's GPA of 2.8 is higher than 88 of the 122 other email apps we grade, and level with 11.
It stands best on free plan and trial (A, above 97 of 122) and worst on platforms and integrations (D, above 0).
K-9 Mail has no paid plan.
On features, ease of use and platforms it scores 2.0 out of 4. Nothing scores higher for less, though at least one tool matches that score at a lower price.
Each grade against the category
Every bar is all 123 email apps we grade, cut by the letter each got. K-9 Mail’s own letter is outlined.
- AValue for moneyAbove 88 of 122, level with 34
- AFree plan and trialAbove 97 of 122, level with 25
- BFeaturesAbove 79 of 122, level with 43
- CEase of useAbove 20 of 122, level with 73
- DPlatforms and integrationsAbove 0 of 122, level with 9
Price against what you get
Each dot is one of 107 email apps. Further left costs less, and higher up scores better on features, ease of use and platforms. Point at a dot to see which tool it is.
Features, ease of use and platforms, averaged
What paid plans start at, a month (each step along is roughly double) →
- The best score at each price
- Has a free plan
- No free plan
Keep K-9 Mail, or make your own?
Keep it
K-9 Mail is free, so making your own would save you nothing.
And it is not the kind of software a weekend replaces. It is one of the better ones too: its GPA of 2.8 is higher than 88 of the 122 other email apps we grade.
What you could not
- An email client: sending, receiving, threading and searching years of mail.
- A real app for Android. Something home-made would be a web page.
- The depth: we grade its features B, which means it covers the whole job.
What this rests on. K-9 Mail’s listing: what it does, where it runs, what it plugs into and what it costs. It is a judgement about the kind of software this is. We have not built a replacement for it, and making your own means looking after it too. How we decide, and every tool’s verdict.
What is K-9 Mail?
K-9 Mail is an open source email app for Android built for handling large volumes of mail. It supports push IMAP, a unified inbox, multiple identities and GPG/PGP signing and encryption. The project's site now announces that Thunderbird for Android is available and describes it as the future of K-9 Mail.
Worth knowing
- Android only; no iOS, desktop or web version is listed.
- The site's banner says Thunderbird for Android is available now and calls it the future of K-9 Mail.
- It is a client for existing mailboxes and does not provide an email address.
Key features
- Push IMAP
- The feature list names push IMAP support, so new messages can arrive without polling on servers that allow it.
- GPG and PGP/MIME
- The site lists GPG and PGP/MIME support for signing and encrypting messages.
- Unified inbox and identities
- A unified inbox, per-account notifications and multiple identities are listed, along with signatures and BCC to self.
- Message handling tools
- Listed tools include message flagging, keyboard shortcuts, attachment saving and emoji support.
- Several ways to install
- The download page offers the Play Store (with a beta channel), F-Droid, GitHub Releases and Amazon.
K-9 Mail pricing
As of Nov 13, 2026, K-9 Mail is free to use.
- Starts at
- Free
- Free plan
- Free to download from Google Play, F-Droid, GitHub Releases or Amazon; no paid plans are listed.
- Free trial
- None listed
| Plan | Price | What you get |
|---|---|---|
| Free | $0 | Open source under the Apache License 2.0; the site has a donate link. |
Read from k9mail.app on Nov 13, 2026. Prices change, so confirm with K-9 Mail before you buy.
K-9 Mail alternatives
- K-9 Mail vs FairEmail
Free plan · from $7.49 one-time
- K-9 Mail vs BlueMail
Free plan · from $35.99/yr
- K-9 Mail vs Aqua Mail
Free plan · from $9.99/mo
- K-9 Mail vs Edison Mail
Free plan · from $14.99/mo
Common questions
Does K-9 Mail have an iPhone app?
No iPhone app was listed when its pages were read on Nov 13, 2026. K-9 Mail is listed for Android.
Does K-9 Mail have a Windows app?
No Windows app was listed when its pages were read on Nov 13, 2026. K-9 Mail is listed for Android.
Is K-9 Mail open source?
Yes. K-9 Mail is open source, according to its own site.
Sources for this page
The prices, plans, platforms and features above were read from these pages on Nov 13, 2026.