The K-9 Mail Insider’s Guide
Everything we know about K-9 Mail in one document: what it costs, its grades, getting a refund, getting help and what else to look at. Read it here, or keep a copy.
K-9 Mail
The Insider’s Guide
Open source email client for Android, now moving to Thunderbird
Every plan, grade, refund rule and rival among email apps, read from K-9 Mail’s own pages.
Made by K-9 Mail · checked Nov 13, 2026 · toolgpa.com
Contents
- 01WelcomeWhat it is, who it suits, its grades and the ten things to know first
- 02What it costsEvery plan, the free plan, ways to pay less and how prices have moved
- 03What it doesIts main features, where it runs, what it works with and who makes it
- 04Where it standsIts grades against its category, and whether to keep it or make your own
- 05The alternativesThe tools it is most often weighed against, side by side
- 06Quick answersThe questions people ask about it, each answered in a line or two
- 07About ToolGPAWho made this guide, what else is on the site, and how to cite it
ToolGPA put this guide together from K-9 Mail’s own pages, its app-store listings and our grades. Every fact in it is on K-9 Mail’s page too, where it is kept up to date. Checked Nov 13, 2026.
Part 01 · Overview
Welcome
What it is, who it suits, its grades and the ten things to know first
2.8
GPA, above 88 of the 122 other email apps we grade
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.
To get you started, here are 8 things to know about K-9 Mail, taken from its own pages and our grades.
You add your accounts and server settings yourself.
- 1
Best for an open-source Android email client
It is Android only and only a client, so it brings no mailbox of its own.
- 2
It is free
K-9 Mail has no paid plan at all. Free to download from Google Play, F-Droid, GitHub Releases or Amazon; no paid plans are listed.
- 3
It runs on Android
Android.
- 4
Push IMAP
The feature list names push IMAP support, so new messages can arrive without polling on servers that allow it.
- 5
GPG and PGP/MIME
The site lists GPG and PGP/MIME support for signing and encrypting messages.
- 6
Unified inbox and identities
A unified inbox, per-account notifications and multiple identities are listed, along with signatures and BCC to self.
- 7
A 2.8 GPA, above 88 of 122
That is against the other email apps we grade, on value, the free plan, features, ease of use and platforms.
- 8
Keep it
K-9 Mail is free, so making your own would save you nothing.
K-9 Mail at a glance
- Pricing
- Free
- Free plan
- Yes
- Free trial
- None stated
- Runs on
- Android
- Made by
- K-9 Mail
- Category
- Email Apps
- Our grade
- 2.8 GPA, good
The report card
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.
| Subject | Grade | Comment |
|---|---|---|
| Value for money | A | Free to download under the Apache 2.0 licence, with no paid plans, and a donate link. |
| Free plan and trial | A | The full app is free from Google Play, F-Droid, GitHub or Amazon. |
| Features | B | Push 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. |
| Ease of use | C | No store rating on record. You add your accounts and server settings yourself. |
| Platforms and integrations | D | Android only: no iPhone, desktop or web version is listed. |
An A is worth 4 points, a B 3, a C 2, a D 1 and an F nothing. The GPA is the average of the five.
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 it 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
Good to know
Good for
- Android users who want an open source IMAP client
- People who sign or encrypt mail with GPG on a phone
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.
Part 02 · Pricing
What it costs
Every plan, the free plan, ways to pay less and how prices have moved
Free
No paid plan at all
K-9 Mail is free to use.
The full app is free from Google Play, F-Droid, GitHub or Amazon.
Free
$0
Open source under the Apache License 2.0; the site has a donate link.
The free plan
Free to download from Google Play, F-Droid, GitHub Releases or Amazon; no paid plans are listed.
Read from k9mail.app on Nov 13, 2026.
Part 03 · Features
What it does
Its main features, where it runs, what it works with and who makes it
1
Place it runs: Android
Open source email client for Android, now moving to Thunderbird. Here is what it does, as its own site describes it, and what it covers: open source, email client.
Push IMAP, GPG and PGP/MIME, a unified inbox, identities and message tools.
- 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.
Where it runs
- Android
What it works with
Its own pages name no integrations.
K-9 Mail is made by K-9 Mail.
Part 04 · Standing
Where it stands
Its grades against its category, and whether to keep it or make your own
88/122
Other email apps it is graded above
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
- AFree plan and trialAbove 97 of 122
- BFeaturesAbove 79 of 122
- CEase of useAbove 20 of 122
- DPlatforms and integrationsAbove 0 of 122
Price against what you get
Each dot is one of 107 email apps. Further left costs less; higher up scores better on features, ease of use and platforms. K-9 Mail is the marked dot.
What paid plans start at, a month (each step along is roughly double) →
Keep it, or make your own?
Whether this is something you could build for yourself with an AI app builder, and what you would give up.
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.
Part 05 · Alternatives
The alternatives
The tools it is most often weighed against, side by side
FairEmail, Thunderbird, BlueMail, Aqua Mail and Edison Mail
The 5 tools K-9 Mail is most often weighed against, with where each one differs from it.
- 2.4GPA
FairEmail
Free plan · from $7.49 one-time
Open source, privacy-oriented email client for Android.
- FairEmail is end-to-end encrypted, according to its own site.
- FairEmail can be bought with a one-time purchase.
- 3.2GPA
Thunderbird
Free
Free, open-source email app for Windows, macOS, Linux and Android.
- Only Thunderbird lists Windows, macOS and Linux apps.
- Thunderbird also covers tasks and calendar.
- 3.2GPA
BlueMail
Free plan · from $35.99/yr
Cross-platform email client with a unified inbox and built-in AI.
- Only BlueMail lists iOS, macOS, Windows and Linux apps.
- K-9 Mail is open source, according to its own site.
- BlueMail is end-to-end encrypted, according to its own site.
- 2.2GPA
Aqua Mail
Free plan · from $9.99/mo
Email app for Android and iOS that handles many accounts at once.
- Only Aqua Mail lists an iOS app.
- K-9 Mail is open source, according to its own site.
- Aqua Mail can be bought with a one-time purchase.
- 3.0GPA
Edison Mail
Free plan · from $14.99/mo
Free multi-account email app with one-tap unsubscribe.
- Only Edison Mail lists iOS and Windows apps.
- K-9 Mail is open source, according to its own site.
- Edison Mail also covers inbox filtering.
Part 06 · Questions
Quick answers
The questions people ask about it, each answered in a line or two
11
Questions, each answered in a line or two
The short version of everything above, for when you only need the answer. Each one is told in full in its part of the guide.
Is K-9 Mail free?
Yes. K-9 Mail is free to use.
How much does K-9 Mail cost?
K-9 Mail lists one plan. Free: $0.
What platforms does K-9 Mail work on?
K-9 Mail is available on Android.
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.
Who makes K-9 Mail?
K-9 Mail is made by a company of the same name.
What are the alternatives to K-9 Mail?
The closest alternatives to K-9 Mail in our directory are FairEmail, Thunderbird, BlueMail, Aqua Mail and Edison Mail.
How does K-9 Mail compare with other 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.
Is K-9 Mail good value for money?
ToolGPA grades K-9 Mail A for value for money. K-9 Mail has no paid plan.
Could I make my own version of K-9 Mail?
K-9 Mail is free, so making your own would save you nothing. And it is not the kind of software a weekend replaces.
Where this guide comes from
The prices, plans, platforms and features were read from K-9 Mail’s own pages on Nov 13, 2026, and the grades were given on Nov 13, 2026. 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.
Every tool we list gets five grades, A to F, each with its reason, and a GPA that averages them. How each is decided is at toolgpa.com/grades. This guide is ToolGPA’s own work; it is not made, paid for or approved by K-9 Mail. Prices change, so check k9mail.app before you buy.
Part 07 · About
About ToolGPA
Who made this guide, what else is on the site, and how to cite it
7,721
Tools graded, in 95 categories
ToolGPA grades software the way a school report grades a pupil: five subjects, a letter for each with the reason written beside it, and a GPA that averages them. Prices, plans and platforms are read from each maker’s own pages and dated, so you always know how fresh a figure is.
Every grade, review and ranking on ToolGPA is our own judgement. No company can pay for a grade or change one. Every tool on the site has a guide like this one, free to download and pass on. It all lives at toolgpa.com.
7,721
tools graded
95
categories
739
price changes on record
579
apps priced in 12 countries
What else is on toolgpa.com
- K-9 Mail, kept up to dateEverything in this guide, with prices and grades as they are todaytoolgpa.com/tools/k-9-mail
- How grades are givenThe rules behind every letter and every GPAtoolgpa.com/grades
- Value chartsWhat each tool costs against what it scores, for every categorytoolgpa.com/charts
- CompareAny two tools side by side, plan by plantoolgpa.com/compare
- Price changesEvery price rise and cut on record, each with its sourcetoolgpa.com/price-changes
- Prices by countryWhat apps cost on the App Store in 12 countriestoolgpa.com/prices-by-country
- Pay lessEvery public discount: yearly billing, students, nonprofitstoolgpa.com/save
- Keep or makeWhich tools are worth paying for, and which you could build yourselftoolgpa.com/keep-or-make
Scan for the live page
Prices and grades as they are today
Quoting this guide?
Please name ToolGPA and link to the live page, so readers can check the figures for themselves:
ToolGPA, "K-9 Mail: The Insider's Guide", checked Nov 13, 2026. https://toolgpa.com/tools/k-9-mail
Know someone choosing between email apps?
Send them this guide: toolgpa.com/tools/k-9-mail/guide
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See our other guides
The best-graded email apps after K-9 Mail, each with an Insider's Guide of its own.
- Email Apps Insider's GuideEvery one of the 126 email apps we grade, compared
- Microsoft Outlook Insider's GuideMicrosoft's email and calendar app for desktop, mobile and web3.6 GPA
- AOL Mail Insider's GuideFree webmail with news and weather in a companion mobile app3.2 GPA
- BlueMail Insider's GuideCross-platform email client with a unified inbox and built-in AI3.2 GPA
Choosing software? Every tool graded, every price dated.
Compare tools at toolgpa.com ›Everything in this guide is ToolGPA’s own summary of what K-9 Mail’s pages, its app-store listings and public reviews said on the dates shown. Grades are our judgement under the rules at toolgpa.com/grades. Every grade, review and ranking on ToolGPA is our own judgement. No company can pay for a grade or change one. K-9 Mail is a trademark of its owner, and this guide is not made, paid for or approved by K-9 Mail. Prices and plans change: check k9mail.app before you buy.