Open Source K-9 Mail Alternatives for Android

There are many alternatives to K-9 Mail for Android if you are looking for a replacement. The best open source Android alternative is Thunderbird. If that doesn't suit you, our users have ranked more than 25 alternatives to K-9 Mail and seven of them are open source and available for Android so hopefully you can find a suitable replacement. Other interesting open source Android alternatives to K-9 Mail are FairEmail, Infomaniak kMail, Ltt.rs and Librem Mail.

filter to find the best alternatives

K-9 Mail alternatives are mainly Email Clients, but if you're looking for Calendar Apps or Contact Managers you can filter on that. Other popular filters include iPhone, Windows, Linux, Android and Android + Open Source. These are just examples - use the filter bar below to find more specific alternatives to K-9 Mail.
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Alternatives list

  1. Thunderbird icon

    Thunderbird

     2530 likes
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    Cross-platform email client supporting multiple identities, chat, and strong filtering. Extend functionality with add-ons like RSS/Atom feed readers and PGP support.

    86 Thunderbird alternatives

    Cost / License

    • Free
    • Open Source

    Application types

    Platforms

    • Mac
    • Windows
    • Linux
    • Android
    • BSD
    • AppImageHub
    • Snapcraft
    • Flathub
    • PortableApps.com
    • F-Droid
    • Haiku
    • Homebrew
    • Chocolatey
    Thunderbird screenshot 1
     
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    37
    Comments about Thunderbird as an Alternative to K-9 Mail
    Tubby 9417
    Positive
    0

    A really great client used by many, popular because it supports almost every mail provider (not proton ?), and mail providers provide documentation to integrate with Thunderbird. I recommand

    Diatomee
    0

    Afaik the Thunderbird for Android and K-9 mail are developed by the same team now and have the same infrastructure under the hood, therefore it doesn't make any difference which one you choose.

    K-9 Mail Icon
    Thunderbird icon

    • Most users think Thunderbird is a great K-9 Mail alternative.

    • Thunderbird is the most popular Windows, Android, Mac & Linux alternative to K-9 Mail.

    • Thunderbird is the most popular Open Source & free alternative to K-9 Mail.

    • Thunderbird is Free and Open SourceK-9 Mail is also Free and Open Source
    • Thunderbird is CustomizableK-9 Mail is not according to our users
  2. FairEmail icon

    FairEmail

     87 likes
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    Open-source, privacy-focused email client offering features such as encryption via OpenPGP and S/MIME, unlimited accounts, a unified inbox, customizable settings, and reformatted emails to prevent phishing. Supports two-way synchronization and provides Pro features for additional customization.

    43 FairEmail alternatives

    Cost / License

    • Freemium (Pay once)
    • Open Source

    Application type

    Platforms

    • Android
    • Android Tablet
    • F-Droid
    Compose message view.
    Setup screen.
    Messages view with dark theme.
     
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    19
    Comments about FairEmail as an Alternative to K-9 Mail
    LongLife
    Positive
    0

    Both are opensource, privacy oriented, free email clients for Android

    K-9 Mail Icon
    FairEmail icon

    • Almost everyone thinks FairEmail is a great K-9 Mail alternative.

    • FairEmail is the most popular Android Tablet alternative to K-9 Mail.

    • FairEmail is Freemium and Open SourceK-9 Mail is Free and Open Source
    • FairEmail is CustomizableK-9 Mail is not according to our users
  4. Infomaniak kMail icon

    Infomaniak kMail

     38 likes
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    Privacy-focused Swiss email system provides 20 GB free storage, supports custom domains and unlimited storage, syncs contacts and calendars, is ad-free, and is part of a secure productivity suite used by over a million users across Europe on all devices.

    42 Infomaniak kMail alternatives

    Cost / License

    • Freemium (Subscription)
    • Open Source

    Application types

    Platforms

    • Online
    • Android
    • iPhone
    • Android Tablet
    • iPad
    • F-Droid
    Infomaniak kMail screenshot 1
     
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    1
    Comments about Infomaniak kMail as an Alternative to K-9 Mail
    Guest
    Negative
    0

    The Infomaniak client only works with Infomaniak mail accounts, while K-9 Mail supports all mail accounts that use the standard IMAP and SMTP protocols

    Review by a new / low-activity user.
    K-9 Mail Icon
    Infomaniak kMail icon
    • Infomaniak kMail is Freemium and Open SourceK-9 Mail is Free and Open Source
  5. Ad
    Screenshot
    Infomaniak kMail icon
    Infomaniak kMail

    Privacy-focused Swiss email system provides 20 GB free storage, supports custom domains and unlimited storage, syncs contacts and calendars, is ad-free, and is part of a secure productivity suite used by over a million users acro...

    https://www.infomaniak.com
    Learn More
  6. Ltt.rs icon

    Ltt.rs

     3 likes
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    No-frills, easy to use, easy to maintain Email client for Android based on the JSON Meta Application Protocol (JMAP).

    56 Ltt.rs alternatives

    Cost / License

    • Free
    • Open Source

    Application type

    Platforms

    • Android
    • F-Droid
    Ltt.rs screenshot 1
    Ltt.rs screenshot 2
    Ltt.rs screenshot 3
     
  7. Librem Mail icon

    Librem Mail

     3 likes
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    End-to-end encrypted email used by nearly everybody already.

    Cost / License

    • Subscription
    • Open Source

    Application type

    Platforms

    • Android
    • Android Tablet
    Librem Mail screenshot 1
    Librem Mail screenshot 2
    Librem Mail screenshot 3
     
  8. monocles mail icon

    monocles mail

     3 likes
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    monocles mail is a fork of the K-9 mail version 5.600 with the old K-9 mail layout.

    Cost / License

    • Freemium (Subscription)
    • Open Source

    Application type

    Platforms

    • Online
    • Android
    • F-Droid
    monocles mail screenshot 1
    monocles mail screenshot 2
    monocles mail screenshot 3
     
  10. Simple Email icon

    Simple Email

     2 likes
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    An open-source email app for Android delivering privacy with a user-friendly minimalist design. It supports multiple accounts, a unified inbox, conversation view, and encryption. Offers two-way sync, offline storage, minimal data use, and battery efficiency. Export settings for easy setup.

    Cost / License

    • Free
    • Open Source

    Application type

    Alerts

    • Discontinued

    Platforms

    • Android
    • F-Droid
    Simple Email screenshot 1
    Simple Email screenshot 2
     
7 of 7 K-9 Mail alternatives