Open Source Thunderbird Alternatives

    The best open source alternative to Thunderbird is K-9 Mail, which is both free and Open Source. If that doesn't suit you, our users have ranked more than 50 alternatives to Thunderbird and many of them is open source so hopefully you can find a suitable replacement. Other interesting open source alternatives to Thunderbird are Evolution (Free, Open Source), Claws Mail (Free, Open Source), SeaMonkey (Free, Open Source) and Mailspring (Freemium, Open Source).

    The list of alternatives was last updated Jun 5, 2021

    Platforms

    • Windows
    • Mac
    • Linux
    • Android
    • iPhone
    • Online
    • Android Tablet
    • iPad
    • BSD
    • Apple Watch
    • OpenPGP
    • S/MIME
    • Software as a Service (SaaS)
    • Self-Hosted
    • Chrome OS
    • Windows S
    • Windows Mobile
    • GNOME
    • Xfce
    • Gmail

    Features

    • Multiple Account support
    • POP3 Support
    • Support for IMAP
    • Portable
    • Calendar
    • Exchange
    • Unified inbox
    • Organize mails
    • Extensible by Plugins/Extensions
    • Customizable
    • Built-in RSS reader
    • Calendar integration
    • Gmail integration
    • Lightweight
    • Contacts
    • Dropbox integration
    • Email tracking
    • Night mode/Dark Theme
    • Threaded Conversations
    • Encrypted Email

    License

    × Clear
    • Free
    • Open Source
    • Paid
    All Filters

    • Open source Android email client with support for multi-folder sync, keyboard shortcuts, and more. View 38 alternatives to K-9 Mail
      Most users think K-9 Mail is a great alternative to Thunderbird.
      • FreeOpen Source
      • Android
      • Android Tablet
      • F-Droid
      K-9 Mail vs Thunderbird
      pros, cons and recent comments
       all • positive • negative      relevance • date
      K-9 Mail works on Android, can use POP3 or IMAP and is easy to use. It's open source with no adverts.
      Top positive comment  about 4 years ago

      12
      open source, stable, essentially bug free, low on resource need, just e-mail without "cool" extra functions you never use.
      Top positive comment  about 3 years ago

      8
      wrong platform. K-9 is for android, Thunderbird is not, so K9 is not a valid alternative for Thunderbird users
      Top negative comment  8 months ago

      5
      Philippe_Hellmuller So far, I dislike the presentation which doesn't allow me to have a global view on my messages and possibly even different accounts. I'm also missing contacts and contact groups. The application looks very much like Outlook that I don't appreciate because of its presentation.
      Positive comment 6 months ago

      0
      Bacma Very pratic and user-friend, but it is too much simple, not personalizable.
      Positive comment 12 months ago

      -2
      Schnatt_App If you seek an alternative for thunderbird, this is the best
      Positive comment over 1 year ago

      -3
      No adverts, configuration is simple and it has black mode,it also works on android 10.
      Positive comment over 1 year ago

      -1
      Show more comments
      7 of 15 comments
    • Evolution is a personal information management application that provides integrated mail, calendaring, address book and task list functionality. View 58 alternatives to Evolution
      Most users think Evolution is a great alternative to Thunderbird.
      • FreeOpen Source
      • Linux
      • BSD
      • S/MIME
      • GNOME
      • OpenPGP
      Evolution vs Thunderbird
      pros, cons and recent comments
      well, I use cinnamon desktop, Thunderbird does not display 24 hour format but AM/PM for starters. Also, I use the built-in acount manager and Thunderbird does not "talk" with that as well.. Evolution does sync my CALDAV and CARDDAV from this. Thunderbird needs plugins for this and these plugins also make Thunderbird unstable (lightning). Since I like to keep things "clean", Evolution is my software of choice ATM...
      Positive comment over 1 year ago

      -1
      Has a nice Gui, works fast and has many options. Still some functions are not intuitive. Good alternative to Thunderbird
      Positive comment about 2 months ago

      0


    • Claws Mail is an email client (and news reader), based on GTK+, featuring Quick response Graceful, and sophisticated interface Easy configuration, intuitive... View 80 alternatives to Claws Mail
      Most users think Claws Mail is a great alternative to Thunderbird.
      • FreeOpen Source
      • Windows
      • Linux
      • BSD
      Claws Mail vs Thunderbird
      pros, cons and recent comments
      3psilon It's a good, lightweight alternative, but the UI is clunky and it misses HTML message composing. You have been warned!
      Top positive comment  almost 4 years ago

      14
      jodumont Despite the style, Claws is super fast and allow you to programs it with Perl and Python which is great for marketing automation.
      Top positive comment  almost 2 years ago

      8
      No HTML compose is the only reason I don't switch to it. We're not in 1980 anymore.
      Top negative comment  over 2 years ago

      13
      very good alternative under linux. I can not say the same under windows since fancy plugin is very buggy.
      Positive comment about 1 year ago

      -1
      Much faster than thunderbird which cloaks on weak machines.
      Positive comment over 3 years ago

      6
      Small and quick and not flooded with choices!
      Positive comment almost 5 years ago

      2
      I like it because of easily customizable key bindings.
      Positive comment about 5 years ago

      0
    • Web-browser, advanced e-mail, newsgroup and feed client, IRC chat, and HTML editing in one application. Itis built on the open source Mozilla Gecko engine, the same code which underlies Thunderbird and is the base for the Firefox browser. View 170 alternatives to SeaMonkey
      Almost everyone thinks SeaMonkey is a great alternative to Thunderbird.
      • FreeOpen Source
      • Mac
      • Windows
      • Linux
      • BSD
      • PortableApps.com
      SeaMonkey vs Thunderbird
      pros, cons and recent comments
      SeaMonkey is both a WEB BROWSER and EMAIL CLIENT. It's the successor of Mozilla Application Suite or Netscape Communicator, resp. Further it includes also a news client program, an HTML editor (SeaMonkey Composer) and an IRC client (ChatZilla).
      Positive comment over 3 years ago

      18
      apostolfaliagas It has all of Thunderbird's features and many more.
      Positive comment over 3 years ago

      13
      More of a web browser than an email client
      Negative comment about 2 years ago

      -7
    • 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. View 39 alternatives to Mailspring
      This alternative is disputed. Mailspring is still a legitimate alternative to Thunderbird, but it might have issues that some users think are important.
      • FreemiumOpen Source
      • Mac
      • Windows
      • Linux
      • Arch Linux
      • Fedora
      • Ubuntu
      Mailspring vs Thunderbird
      pros, cons and recent comments
      riskaasmara Simple, more streamlined UI and easily customizable.
      Top positive comment  over 2 years ago

      3
      3psilon Great alternative, especially for casual users. Simple, streamlined UI, feels fresh.
      Top positive comment  about 3 years ago

      0
      Need to create an account on a third-party company to access your email.
      Top negative comment  over 2 years ago

      48
      peterbro nice interface (if you are talking about the feature, kcontact/kmail is the best, but this has a nice interface)
      Positive comment over 3 years ago

      -2
      Very simple, perfect IU and possibility to follow what happen to your emails.
      Positive comment over 3 years ago

      -2
      bengotow Supports Linux and all IMAP providers, offers shortcut customization, extensible via plugins.
      Positive comment over 3 years ago

      -3


    • Geary is an email application built around conversations, for the GNOME 3 desktop. View 49 alternatives to Geary
      Some users think Geary is a great alternative to Thunderbird, some don't.
      • FreeOpen Source
      • Linux
      • Chrome OS
      • BSD
      • GNOME
      Geary vs Thunderbird
      pros, cons and recent comments
      Only IMAP. No support for local folders.
      Negative comment over 2 years ago

      1
      Doesn't have an address book
      Negative comment about 4 years ago

      0
      Easy to set up. Thunderbird doesn't connect anymore with hotmail and yahoo. No address book.
      Positive comment almost 4 years ago

      -21
    • Mutt is a small but very powerful text-based mail client for Unix operating systems. View 52 alternatives to Mutt
      Most users think Mutt is a great alternative to Thunderbird.
      No screenshots yet
      • FreeOpen Source
      • Mac
      • Windows
      • Linux
      • Xfce
      Mutt vs Thunderbird
      pros, cons and recent comments
      Thunderbird users want a GUI mail application. Mutt is a command line mail application. They are both good and both popular, but very much apples and oranges.
      Negative comment about 1 year ago

      10
    • FairEmail is a privacy-focused email client with a setup wizard that helpfully walks you through the steps to use it with any email provider. View 38 alternatives to FairEmail
      Most users think FairEmail is a great alternative to Thunderbird.
      • FreemiumOpen Source
      • Android
      • Android Tablet
      FairEmail vs Thunderbird
      pros, cons and recent comments
      wrong platform. FairEmail is not an alternative for Thunderbird users because it only runs on android. Thunderbird is for desktop operating systems only.
      Negative comment 8 months ago

      -4
    • Sylpheed is a simple, lightweight but featureful, and easy-to-use e-mail client (mailer, MUA). View 43 alternatives to Sylpheed
      Most users think Sylpheed is a great alternative to Thunderbird.
      • FreeOpen Source
      • Mac
      • Windows
      • Linux
      • BSD
      • PortableApps.com
      Sylpheed vs Thunderbird
      pros, cons and recent comments
      It doesn't encrypt password storage and doesn't have Master Password function
      Negative comment about 2 years ago

      2
    • KMail is the email component of Kontact, the integrated personal information manager of KDE. Kontact is a personal information manager and groupware software suite for KDE. View 55 alternatives to Kontact - KMail
      Most users think Kontact - KMail is a great alternative to Thunderbird.
      • FreeOpen Source
      • Linux
      • BSD
    Showing 10 of 33 alternatives