Alternatives to Thunderbird
Mozilla’s desktop mail client, with calendar, contacts and a unified inbox, funded by donations rather than ads. The listings below can replace it for an important use case. Each note says what changes if you switch.
The original
Thunderbird
Mozilla’s desktop mail client, with calendar, contacts and a unified inbox, funded by donations rather than ads.
Replacements
Listings that take over the same core job as Thunderbird.
Betterbird
A Thunderbird fork that ships extra fixes and features, and can run side by side on the same profile.
Betterbird is a Thunderbird fork with extra fixes and features that runs on the same profile, but it is a small volunteer project following Thunderbird's ESR releases.
Microsoft Outlook
Microsoft's email, calendar and contacts app for desktop, mobile and the web.
Microsoft Outlook adds web and mobile versions and Microsoft 365 integration, but it is closed source, tied to Microsoft services and some features need a paid plan.
Apple Mail
The email app built into macOS, iOS and iPadOS for reading mail from several providers.
Apple Mail comes preinstalled on Mac, iPhone and iPad and works with iCloud Hide My Email, but it is closed source and has no Windows or Linux version.
eM Client
A polished commercial mail, calendar and contacts client for Windows and Mac, with a free tier capped at two accounts.
eM Client offers a polished closed-source mail, calendar and contacts client for Windows and Mac, with a free tier capped at two accounts and no Linux version.
Mailspring
A desktop mail client with a unified inbox, snooze and send later, whose paid tier adds read receipts.
Mailspring provides a unified inbox, snooze and send later on Windows, macOS and Linux under GPL-3.0, but it is Electron-based and has no built-in calendar.
Evolution
GNOME's mail, calendar, contacts and tasks suite, and the usual answer for Exchange on Linux.
Evolution combines mail, calendar, contacts and tasks on Linux only, with an Exchange Web Services plugin for Microsoft 365, and is heavier and slower to start.
KMail
KDE's email client with IMAP, filtering and OpenPGP support.
KMail is KDE's Linux client with integrated OpenPGP and S/MIME and shared Kontact calendar and contacts, but it depends on the often troublesome Akonadi storage service.
Claws Mail
A fast, keyboard-driven email client that loads a hundred thousand message folder without thinking about it.
Claws Mail is a fast, keyboard-driven GPL client that handles huge folders well, but it composes plain text by default and only has a vCalendar plugin.
Also worth comparing
These listings name Thunderbird as their own alternative, so the relationship runs both ways.
aerc
A terminal email client with vim-style keys, an embedded terminal for composing, and first-class support for git email workflows.
Thunderbird is a graphical desktop client for Windows, macOS and Linux with calendar, contacts, built-in OpenPGP and add-ons, giving up aerc's terminal and patch workflow focus.
Aqua Mail
An Android email app that manages Gmail, Outlook, Exchange, iCloud and any IMAP or POP3 account.
Thunderbird offers a free, open-source Android app, though that app is a separate product from the desktop client and does not share a profile with it.
Balsa
A lightweight GTK email client for the GNOME desktop.
Thunderbird is heavier but adds calendar, contacts, OpenPGP and add-ons, and runs on Windows and macOS as well as Linux.
BlueMail
Cross-platform email and calendar client with a unified inbox.
Thunderbird is free and open source with a unified inbox, calendar and built-in OpenPGP on Windows, macOS, Linux and Android, though it has no iOS app.
Canary Mail
Encrypted email client with AI features across desktop and mobile.
Thunderbird is free and open source with built-in OpenPGP, calendar and Linux support, but has no iOS app and no AI triage features.
FairEmail
An open-source, privacy-oriented email app for Android that works with almost any email provider.
Thunderbird offers a free open-source Android app from Mozilla alongside desktop clients, though the Android app does not share a profile with the desktop.
Geary
GNOME email client built around conversation threads.
Thunderbird adds calendar, tasks, built-in OpenPGP and an add-on ecosystem on Windows, macOS, Linux and Android, with a denser interface.
K-9 Mail
Open-source Android email client built for handling large volumes of mail.
Thunderbird's official Android app is built on K-9 Mail, with Mozilla backing, and the desktop client adds calendar and OpenPGP though it does not share a profile.
Kiwi for Gmail
A desktop app for Mac and Windows that runs Gmail and Google Workspace outside the browser.
Thunderbird is a free open-source client for Gmail and any other account with calendar and contacts, on Windows, macOS and Linux, without Google Workspace app shortcuts.
Kontact
KDE's personal information manager that combines mail, calendar, contacts and news in one window.
Thunderbird combines mail, calendar, contacts and tasks with add-ons and built-in OpenPGP, and also runs on Windows, macOS and Android.
Mailbird
Desktop email client for Windows and macOS with a unified inbox.
Thunderbird is free and open source, runs on Linux as well as Windows and macOS, and adds calendar, tasks and built-in OpenPGP, though its interface feels dense.
MailMate
A keyboard-driven IMAP email client for macOS with Markdown composition and advanced search.
Thunderbird is free and open source on macOS, Windows and Linux with built-in OpenPGP, calendar and contacts, but its interface can feel dense.
Pegasus Mail
A long-running free desktop email client for Windows, maintained alongside the Mercury mail server.
Thunderbird is free and open source under MPL-2.0, runs on Windows, macOS and Linux, and adds a calendar, unified inbox and built-in OpenPGP.
Spark Mail
Smart email client that auto-sorts inboxes and drafts AI-powered replies.
Thunderbird is free and open source with Linux support, calendar and built-in OpenPGP, but has no iOS app and no AI reply drafting.
Spike
Turns email into a chat-like interface with message bubbles instead of a list.
Thunderbird is free and open source with a classic list layout, calendar and OpenPGP, and runs on Linux, but has no iOS app.
The Bat!
A Windows desktop email client that keeps mail locally, with on-disk encryption and end-to-end encryption.
Thunderbird is free and open source under MPL-2.0, runs on Windows, macOS, Linux and Android, and adds calendar, contacts and built-in OpenPGP.
Wino Mail
Native Windows mail and calendar client for Outlook, Gmail and IMAP accounts.
Thunderbird runs on Windows, macOS, Linux and Android with mail, calendar, contacts and tasks, plus built-in OpenPGP, but its interface can feel dense.
Similar software
Related functionality, not a direct replacement.
Proton Mail Bridge
Local gateway that lets standard mail clients read a Proton Mail account.
OfflineIMAP
Synchronises IMAP accounts into local Maildir folders.
MailStore Home
Free Windows email archiver for IMAP, Exchange and PST files.
