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Thunderbird

Free, open-source email, calendar and contacts app for Windows, Mac, Linux and Android.

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About Thunderbird

Thunderbird is the long-running open-source mail client from MZLA, a subsidiary of the Mozilla Foundation. The desktop app for Windows, Mac and Linux handles many IMAP, POP and Exchange-compatible accounts, with a unified inbox, calendar, address book, message filters, OpenPGP encryption built in and a large catalogue of add-ons. The Android app is the former K-9 Mail, rebranded after Thunderbird took over the project, and an iOS version has been in development. Everything is free and funded by user donations, with no ads or data collection. Recent releases have modernised the interface, which used to look dated, and added a monthly release channel. Its weaknesses are that Microsoft Exchange support still needs care for some setups, add-ons can break between major versions, and there is no web version. For people who want a capable desktop client they control, it remains the default recommendation.

Best for: Desktop users who want a free, private, customisable mail and calendar app.

Pros and cons

What works

  • Free, open source and funded by donations, with no ads
  • Built-in OpenPGP, calendar, filters and many add-ons
  • Runs on Windows, Mac, Linux and Android

Why people leave

  • No web version and no released iOS app yet
  • Add-ons sometimes break after major updates
  • Exchange setups can need extra configuration

Top Thunderbird alternatives

See all 6
  1. 1Mailspring logo
    Mailspring

    An open-source desktop client with a more modern look and optional Pro features.

    66.5
  2. 2eM Client logo
    eM Client

    A polished Windows and Mac client with strong Exchange and calendar support.

    62.6
  3. 3FairEmail logo
    FairEmail

    Open-source, privacy-focused Android client with very deep settings.

    59.6
  4. 4Geary logo
    Geary

    A lighter, conversation-based open-source client for the GNOME desktop.

    57.2
  5. 5NeoMutt logo
    NeoMutt

    A terminal mail reader for people who want full keyboard control and scripting.

    55.3

Why people left Thunderbird

In reviewers' own words, from reviews of the apps they moved to. These are their opinions, not ours.

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Reviews

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Thunderbird: common questions

Is Thunderbird free?

Yes. Thunderbird is free, open-source software.

Is Thunderbird open source?

Yes. The source code is on GitHub at thunderbird/thunderbird-android.

What platforms does Thunderbird run on?

Thunderbird is available for Windows, macOS, Linux and Android.

What are the best alternatives to Thunderbird?

The highest-ranked Thunderbird alternatives right now are Mailspring, eM Client and FairEmail. See the full ranked list for pricing, platforms and verified facts.

See all 6 Thunderbird alternatives