The Best K-9 Mail AlternativesTop Email Clients and other similar apps like K-9 Mail

K-9 Mail is described as 'K-9 is an open source email client for Android with multi-folder sync, email signatures, Bcc-to-self, return-address configuration, keyboard shortcuts, Exchange Support, message flagging, IMAP deletes, saving attachments, configurable notifications and more' and is a very popular Email Client in the office & productivity category. There are more than 25 alternatives to K-9 Mail for a variety of platforms, including Android, Windows, Mac, iPhone and Android Tablet apps. The best K-9 Mail alternative is Thunderbird, which is both free and Open Source. Other great apps like K-9 Mail are FairEmail, Betterbird, Evolution and Microsoft Outlook.

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 Android + Open Source. These are just examples - use the filter bar below to find more specific alternatives to K-9 Mail.
K-9 Mail iconK-9 Mail
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  • ...

K-9 is an open source email client for Android with multi-folder sync, email signatures, Bcc-to-self, return-address configuration, keyboard shortcuts, Exchange Support, message flagging, IMAP deletes, saving attachments,...

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K-9 Mail alternatives page was last updated Mar 13, 2025
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  1. Thunderbird icon

    Thunderbird

     2468 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.

    84 Thunderbird alternatives

    License model

    • Free • Open Source

    Application types

    Country of Origin

    • US flagUnited States

    Platforms

    • Mac
    • Windows
    • Linux
    • Android
    • BSD
    • AppImageHub
    • Snapcraft
    • Flathub
    • PortableApps.com
    • F-Droid
    • Haiku
    • Homebrew
    • Chocolatey
    Thunderbird screenshot 1

    Properties

    1.  Customizable
    2.  Intuitive Interface
    3.  Privacy focused

    Features

    1.  Extensible by Plugins/Extensions
    2.  Multiple Account support
    3.  IMAP Support
    4.  Calendar Integration
    5.  SMTP Support
    6.  Email Organizer
    7.  Add-ons
    8.  Built-in RSS reader
    9.  POP3 Support
    10.  Graphical User Interface
    11.  Dark Mode
    12. Google Calendar icon  Google Calendar integration

    Thunderbird VS K-9 Mail

     
    Comments about Thunderbird as an Alternative to K-9 Mail
    Tubby 9417
    Positive Oct 11, 2023
    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

    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

     79 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

    License model

    • Freemium • Open Source

    Application type

    Country of Origin

    • NL flagNetherlands
    • European Union flagEU

    Platforms

    • Android
    • Android Tablet
    • F-Droid
    Compose message view.
    Setup screen.
    Messages view with dark theme.

    Properties

    1.  Privacy focused
    2.  Customizable
    3.  Lightweight

    Features

    1.  Multiple Account support
    2.  Email Notifications
    3.  PGP Encryption
    4.  Extensive settings menu
    5.  IMAP Support
    6.  Notifications
    7.  No Tracking
    8.  Works Offline
    9.  Ad-free
    10.  Unified inbox
    11.  Dark Mode
    12.  S/MIME Support

    FairEmail VS K-9 Mail

     
    Comments about FairEmail as an Alternative to K-9 Mail
    LongLife
    Positive Feb 8, 2024
    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 Privacy focused and CustomizableK-9 Mail is not according to our users
  4. Betterbird icon

    Betterbird

     53 likes
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    Betterbird, a soft fork of Mozilla Thunderbird, improves user experience with advanced features, bug fixes, security patches, and multi-row descriptions similar to Outlook. Compatible with multiple platforms and can be used alongside Thunderbird, sharing the same profile.

    27 Betterbird alternatives

    License model

    • Free • Open Source

    Application types

    Country of Origin

    • DE flagGermany
    • European Union flagEU

    Platforms

    • Mac
    • Windows
    • Linux
    • Flathub
    • Chocolatey
    Betterbird screenshot 1

    Properties

    1.  Privacy focused
    2.  Support for Themes
    3.  Lightweight

    Features

    1.  Multiple Account support
    2.  Extensible by Plugins/Extensions
    3.  Works Offline
    4.  Unified inbox
    5.  Spam Filter
    6.  Calendar Integration
    7.  No Tracking
    8.  Ad-free
    9.  SMTP Support
    10.  POP3 Support
    11.  Portable
    12.  IMAP Support

    Betterbird VS K-9 Mail

     
  5. Ad
    Screenshot
    Infomaniak kMail icon
    Infomaniak kMail

    Infomaniak’s Mail Service is a secure emailing system hosted in Switzerland and is the best (free) alternative to the web giants. Infomaniak’s emailing service is used by more than a million companies and individuals throughout E...

    https://www.infomaniak.com
    Learn More
  6. Evolution icon

    Evolution

     203 likes
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    Evolution is a personal information management application that provides integrated mail, calendaring, address book and task list functionality.

    72 Evolution alternatives

    License model

    • Free • Open Source

    Application types

    Country of Origin

    • US flagUnited States

    Platforms

    • Linux
    • BSD
    • Flathub
    • S/MIME
    • GNOME
    • OpenPGP
    Mail

    Top Evolution Features

    1.  Calendar Integration
    2.  Contacts
    3.  CalDAV Support
    4.  Calendar View
    5.  Ad-free
    6.  Spam Filter
    7.  Multiple Account support
    8. Google Calendar icon  Sync with Google Calendar
    9.  Extensible by Plugins/Extensions
    10.  Dark Mode
    11.  Works Offline
    12.  GPG Encryption

    Evolution VS K-9 Mail

     
  7. Microsoft Outlook icon

    Microsoft Outlook

     397 likes
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    Streamline emails, calendars, contacts, and task management with a smart inbox prioritizing critical messages. Includes calendar scheduling, third-party app integration like Facebook, Dropbox, and Trello, and support for Microsoft Exchange, Outlook.com, and Gmail, ensuring efficient task and email handling.

    128 Microsoft Outlook alternatives

    License model

    Application types

    Country of Origin

    • US flagUnited States

    Platforms

    • Mac
    • Windows
    • Online
    • Android
    • iPhone
    • Android Tablet
    • iPad
    • Apple Watch
    • Android Wear
    Outlook 365 on Windows

    Top Microsoft Outlook Features

    1.  Exchange
    2.  Native application
    3.  Email Organizer
    4.  Calendar Integration
    5.  Calendar View
    6.  Cloud Sync
    7.  Support for @mentions
    8.  Unified inbox
    9.  Multiple Account support
    10.  Works Offline
    11.  Support for Aliases
    12.  Dark Mode

    Microsoft Outlook VS K-9 Mail

     
    Comments about Microsoft Outlook as an Alternative to K-9 Mail
    Guest
    Negative May 14, 2019
    5

    Microsoft Office Outlook has more vulnerabilities and so far, seems more of a memory hogger on my device than K-9 Mail. Thank you, K-9 Mail!

    Guest
    Negative Oct 5, 2024
    0

    If you use outlook for another email it will strore the password on a Microsoft server

    K-9 Mail Icon
    Microsoft Outlook icon

    • This alternative is disputed. Microsoft Outlook is a legitimate K-9 Mail alternative, but it might have issues that some users think are important.

    • Microsoft Outlook is the most popular Web-based, iPhone & iPad alternative to K-9 Mail.

    • Microsoft Outlook is the most popular commercial alternative to K-9 Mail.

    • Microsoft Outlook is Paid and ProprietaryK-9 Mail is Free and Open Source
  8. Spark Mail icon

    Spark Mail

     130 likes
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    E-mail app with all the great features: swipes (long/short), snooze, add (multiple) attachments from the cloud, support for various e-mail services and more.

    61 Spark Mail alternatives

    License model

    • Freemium • Proprietary

    Application types

    Country of Origin

    • UA flagUkraine

    Platforms

    • Mac
    • Windows
    • Android
    • iPhone
    • iPad
    • Apple Watch
    Spark Mail screenshot 1

    Top Spark Mail Features

    1.  Multiple Account support
    2.  Email Scheduling
    3.  Snooze Mail
    4.  Cloud Sync
    5.  Calendar Integration
    6.  Dark Mode
    7.  Email Organizer
    8.  Unified inbox
    9.  Works Offline
    10.  Mail Filtering
    11.  Ad-free
    12. Google Calendar icon  Sync with Google Calendar

    Spark Mail VS K-9 Mail

     
    Comments about Spark Mail as an Alternative to K-9 Mail
    abogawat
    Positive Oct 31, 2023
    0

    Spark is one of the most polished email clients out there, with multi-platform support and an excellent feature set. The free version is good enough for most people.

    K-9 Mail Icon
    Spark Mail icon

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

    • Spark Mail is Freemium and ProprietaryK-9 Mail is Free and Open Source
  10. Mailspring icon

    Mailspring

     107 likes
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    Boost your productivity and send better email with Mailspring, a beautiful, fast email client for Mac, Windows, and Linux. Mailspring is free to use and an optional pro version adds read receipts, send later, reminders and more.

    42 Mailspring alternatives

    License model

    • Freemium • Open Source

    Application types

    Country of Origin

    • US flagUnited States

    Platforms

    • Mac
    • Windows
    • Linux
    • Arch Linux
    • Fedora
    • Ubuntu
    Clean design with integrated search and swipe gestures

    Properties

    1.  Customizable
    2.  User friendly
    3.  Support for Themes

    Features

    1.  Unified inbox
    2.  Multiple Account support
    3.  Dark Mode
    4.  Email tracking
    5.  Snooze Mail
    6.  Ad-free
    7.  Built-in translation
    8.  Theme Customization
    9.  IMAP Support
    10.  Extensible by Plugins/Extensions
    11.  Email Organizer
    12.  Keyboard Shortcuts

    Mailspring VS K-9 Mail

     
  11. Claws Mail icon

    Claws Mail

     102 likes
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    Claws Mail is an email client (and news reader), based on GTK+, featuring

    Quick response Graceful, and sophisticated interface Easy configuration, intuitive operation Abundant features Extensibility Robustness and stability.

    62 Claws Mail alternatives

    License model

    • Free • Open Source

    Application types

    Platforms

    • Windows
    • Linux
    • BSD
    The main window

    Properties

    1.  Lightweight
    2.  Privacy focused
    3.  Customizable

    Features

    1.  Extensible by Plugins/Extensions
    2.  Multiple Account support
    3.  IMAP Support
    4.  Spam Filter
    5.  Works Offline
    6.  No registration required
    7.  Ad-free
    8.  Dark Mode
    9.  Calendar Integration
    10.  Portable
    11.  GPG Encryption
    12.  Built-in RSS reader

    Claws Mail VS K-9 Mail

     
  12. Apple Mail icon

    Apple Mail

     237 likes
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    There’s big news attached. The best way to manage email on a Mac, according to Apple.

    72 Apple Mail alternatives

    License model

    • Free • Proprietary

    Application type

    Country of Origin

    • US flagUnited States

    Platforms

    • Mac
    • iPhone
    • iPad
    • Online
    • Apple Watch
    Apple Mail screenshot 1

    Properties

    1.  Customizable

    Features

    1.  Bundled with macOS
    2.  Email Organizer
    3.  Multiple Account support
    4.  Dark Mode
    5.  Spam Filter
    6.  CardDAV Support
    7.  Exchange
    8.  CalDAV Support
    9.  Rich text editing
    10.  Encrypted Email

    Apple Mail VS K-9 Mail

     
  13. Canary Mail icon

    Canary Mail

     26 likes
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    Canary can write your emails, prioritize what needs attention, silence spam & much more. Say hello to your Inbox Copilot!

    61 Canary Mail alternatives

    License model

    • Freemium • Proprietary

    Application types

    Country of Origin

    • GB flagUnited Kingdom

    Platforms

    • Mac
    • Windows
    • Android
    • iPhone
    • Android Tablet
    • iPad
    • Apple Watch
    iOS-1

    Properties

    1.  Privacy focused
    2.  Lightweight

    Features

    1.  End-to-End Encryption
    2.  Unified inbox
    3.  PGP Encryption
    4.  Multiple Account support
    5.  AI-Powered
    6.  GPG Encryption
    7.  Dark Mode
    8.  No Tracking
    9.  Cloud Sync
    10.  Ad-free
    11.  Reminders
    12.  Encrypted Email

    Canary Mail VS K-9 Mail

     
  14. Infomaniak kMail icon

    Infomaniak kMail

     32 likes
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    Infomaniak’s Mail Service is a secure emailing system hosted in Switzerland and is the best (free) alternative to the web giants. Infomaniak’s emailing service is used by more than a million companies and individuals throughout Europe.

    41 Infomaniak kMail alternatives

    License model

    • Freemium • Open Source

    Application types

    Country of Origin

    • CH flagSwitzerland

    Platforms

    • Online
    • Android
    • iPhone
    • Android Tablet
    • iPad
    • F-Droid
    Infomaniak kMail screenshot 1

    Properties

    1.  Privacy focused

    Features

    1.  Ad-free
    2.  No Tracking
    3.  Portable
    4.  Calendar Integration
    5.  Multiple Account support
    6.  Cloud Sync
    7.  Support for Aliases
    8.  Real time collaboration
    9.  Secure mail
    10.  Sync Contacts
    11.  Calendar Sync
    12.  CardDAV Support

    Infomaniak kMail VS K-9 Mail

     
    Comments about Infomaniak kMail as an Alternative to K-9 Mail
    Guest
    Negative Jul 21, 2024
    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

    K-9 Mail Icon
    Infomaniak kMail icon
    • Infomaniak kMail is Freemium and Open SourceK-9 Mail is Free and Open Source
    • Infomaniak kMail is Privacy focusedK-9 Mail is not according to our users
  15. BlueMail icon

    BlueMail

     33 likes
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    BlueMail is a modern, mobile first, powerful Email management tool with a sleek design, unified inbox and support for all your accounts: IMAP,Exchange,POP3.

    30 BlueMail alternatives

    License model

    • Free Personal • Proprietary

    Application type

    Country of Origin

    • US flagUnited States

    Platforms

    • Mac
    • Windows
    • Linux
    • Android
    • iPhone
    • Chrome OS
    • Android Tablet
    • iPad
    • Apple Watch
    BlueMail screenshot 1
    BlueMail screenshot 2
    BlueMail screenshot 3

    Properties

    1.  Lightweight

    Features

    1.  Unified inbox
    2.  IMAP Support
    3.  Ad-free
    4.  GDPR Compliant
    5.  Multiple Account support
    6.  Calendar Integration
    7.  POP3 Support

    BlueMail VS K-9 Mail

     
12 of 41 K-9 Mail alternatives