Aqua Mail vs K-9 Mail (2026): which should you pick?
As of Nov 13, 2026, K-9 Mail grades higher than Aqua Mail: 2.8 against 2.2 out of 4.0.
Checked Nov 13, 2026 · graded Nov 13, 2026 by ToolGPA
Aqua Mail grades higher on platforms. K-9 Mail grades higher on value for money, the free plan and features. They get the same grade on ease of use.
Price, platforms and features side by side. The table says where each price was read and when.
Aqua Mail
Email app for Android and iOS that handles many accounts at once
Which one is for you
Pick Aqua Mail if
- Fits if you read three or four mailboxes from different providers on your phone
- Works for people who would sooner pay once than every month
Look elsewhere if
- Skip it if you want a desktop or web app too, as it's phones only
- Tight if you stay free: one account, with ads and only part of the features
- Pricey if you go monthly, at $9.99 a month
- Watch out: the $1 first-term offer renews at $9.99 a month
- Watch out: the pricing page loads prices with JavaScript, so the yearly view is not on record
Pick K-9 Mail if
- Fits if you read several mailboxes on one Android phone
- Works for people who want GPG and open-source code
Look elsewhere if
- 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
How we grade them
| 2.2GPAAqua MailFair | 2.8GPAK-9 MailGood | |
|---|---|---|
| Value for money | BPremium is $9.99 a month, but the family plan works out at $1.99 a head and the one-off is $99.99. That's under two years of what the typical email app charges, so the one-off is the way in. | AFree to download under the Apache 2.0 licence, with no paid plans, and a donate link. |
| Free plan and trial | CFree covers one account, with ads and only some of the features. Add a second mailbox and you're paying. | AThe full app is free from Google Play, F-Droid, GitHub or Amazon. |
| Features | CUnlimited accounts on paid plans, manual IMAP and POP3, colour-coding and scheduled backups. It does the phone-mail job and the listing shows no real gap, but nothing here goes past the basics. | BPush 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 | CNo store rating on record. You still add each mailbox yourself, and there are hundreds of settings to wade through if you go looking. | CNo store rating on record. You add your accounts and server settings yourself. |
| Platforms and integrations | CAndroid and iPhone only. No desktop app and no web version, so it's one family of devices. | DAndroid only: no iPhone, desktop or web version is listed. |
| Best for | one inbox for many mailboxes on a phone | an open-source Android email client |
The GPA is the average of the five grades: an A is 4 points, an F is none. The full reasons are on each tool's page: Aqua Mail and K-9 Mail. How we grade
Price against what you get
Aqua Mail starts at $9.99 a month and scores 2.0 out of 4 on features, ease of use and platforms. K-9 Mail has no paid plan and scores 2.0.
They score the same, and K-9 Mail starts $9.99 a month lower. Of the other email apps on the chart, 52 score higher than Aqua Mail for less, and none scores higher than K-9 Mail for less.
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
Where they differ
- Aqua Mail can be bought with a one-time purchase.
- K-9 Mail is open source, according to its own site.
At a glance
| Aqua Mail | K-9 Mail | |
|---|---|---|
| Pricing | Free plan | Free |
| Starts at | $9.99 per month (Premium) | Free |
| Free plan | Free: one account with ads and limited access to key, advanced and customization features. | Free to download from Google Play, F-Droid, GitHub Releases or Amazon; no paid plans are listed. |
| Free trial | None listed | None listed |
| iOS | ||
| Android | ||
| Made by | Aqua Mail | K-9 Mail |
| Price read from | aqua-mail.com | k9mail.app |
| Checked | Nov 13, 2026 | Nov 13, 2026 |
Worth knowing
Aqua Mail
- The free version is limited to one account and shows ads.
- The pricing page loads prices with JavaScript; a Yearly toggle exists that was not captured, so only the monthly view is recorded.
- The $1 first-term offer renews at $9.99 a month, per the page's footnote.
- Phone apps only; no desktop client is listed.
K-9 Mail
- 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
Aqua Mail
- Many accounts, one inbox
- Supports unlimited accounts on paid plans, covering major providers and manually entered IMAP or POP3 servers.
- Privacy approach
- The vendor says the app is not cloud based and does not store passwords or emails on its servers.
- Customization
- The site advertises hundreds of settings for personalizing the mail experience, such as color-coding accounts.
- Scheduled backups
- The vendor's blog covers scheduled backups so messages are not lost if an account or phone changes.
- Android and iOS
- Download buttons for both platforms are on the site, and the app lists in-app purchases on Google Play.
K-9 Mail
- 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.
Plans
Aqua Mail
Free$0
One account, with ads and limited access to features.
Premium$9.99
per month
Unlimited accounts, no ads and full access; the page also offers a first-term promotion.
Family$1.99
per user / month, billed annually ($144 a year)
For up to 6 users; unlimited accounts, no ads and full access.
One-off$99.99
one-time
Unlimited accounts, no ads and full access; shown with $199 crossed out.
K-9 Mail
Free$0
Open source under the Apache License 2.0; the site has a donate link.
Ways to pay less
Aqua Mail
- Other savings
First term for $1, 80% off Premium
The pricing page promotes Aqua Mail for only $1 with the footnote that it renews at $9.99 a month, cancel anytime.
K-9 Mail
No public discounts listed.
Common questions
Which is cheaper, Aqua Mail or K-9 Mail?
As of Nov 13, 2026, K-9 Mail is cheaper to start with: it is free, against $9.99 a month for Aqua Mail. Aqua Mail starts at $9.99 per month (Premium), and K-9 Mail is free.
Which has a free plan, Aqua Mail or K-9 Mail?
As of Nov 13, 2026, both Aqua Mail and K-9 Mail have a free plan.
Which platforms do Aqua Mail and K-9 Mail run on?
As of Nov 13, 2026, only Aqua Mail lists an iOS app. Both list an Android app. A platform missing from a listing is one its maker's pages did not mention.
More comparisons
How this page was made
- The verdict at the top follows a fixed rule. When both tools are in the same category and either is in our top three for it, the verdict follows that ranking: the higher-placed tool is our pick. The top three weigh who each tool suits as well as its grades, so a pick can go against the GPA. Otherwise the page does not pick one and says which grades higher: the higher GPA first; on a tie, the one with a free plan, then the one that starts cheaper in dollars a month, counted the same way for both; if they are still level, what the choice depends on.
- The grades are our own, from each tool’s review or report card. The GPA is their average.
- Prices, plans and platforms come from each tool’s listing. The table above says where each price was read and when.
- The differences and the answers to the questions are worked out from those listings.