Disclosure: we make Canary Mail. Thunderbird is a very good free app, and we say where it beats ours. Features were checked on thunderbird.net, the Thunderbird blog and canarymail.io on October 16, 2026.
Short answer: choose Thunderbird if you want a free, open-source desktop client, use Linux, or like to customize everything with add-ons; it also has encryption and a calendar built in. Choose Canary Mail if you want the same polished app on your iPhone, iPad and Mac as well as Windows and Android, AI that sorts and writes email, and less setup. Thunderbird's iPhone app is only an early TestFlight beta; Canary has no Linux app.
Canary Mail vs Thunderbird at a glance
| Canary Mail | Thunderbird | |
|---|---|---|
| Price | Free; Growth $36/year; Pro+ $100/year; lifetime $100 or $300 | Free, funded by donations |
| Open source | No | Yes |
| Desktop | Mac, Windows | Windows, Mac, Linux |
| Mobile | iPhone, iPad, Android | Android; iPhone app in public beta on TestFlight |
| Accounts | Gmail, Outlook, Microsoft 365, Exchange, iCloud, Yahoo, any IMAP | Any IMAP or POP account, Gmail, Outlook, Microsoft 365 |
| AI | AI sorting free; AI writing and summaries on Growth | No AI writing or summaries listed among its features |
| Encryption | PGP and SecureSend on Pro+ | OpenPGP and S/MIME built in, free |
| Calendar | Full on Mac, iPhone, iPad; Gmail calendars on Windows; none on Android | Built in, with contacts and tasks |
| Customization | Light and dark themes, custom thread actions and alerts | Add-ons, themes and a highly configurable layout |
Price and licence
Thunderbird costs nothing, has no paid tier for the app and shows no ads. It's open source, developed by a Mozilla subsidiary and funded mostly by user donations. That is hard to argue with.
Canary Mail is a commercial app. The free plan covers unlimited accounts on two devices with AI inbox sorting. Growth ($36 a year) adds AI writing and summaries, read receipts, send later and five devices; Pro+ ($100 a year) adds PGP, SecureSend and phishing protection. Both are also sold as one-time lifetime licences ($100 and $300), with a 7-day trial and no monthly option.
Verdict: Thunderbird. Free and open source beats any price.
Inbox, search and AI
Thunderbird gives you a unified inbox, tags, saved searches, message filters and fast full-text search across every account. It's powerful, but you set most of it up yourself, and the layout feels more traditional than modern apps. Its site doesn't list AI writing or summaries as features; it stresses instead that Thunderbird doesn't collect personal data or train AI on your mail.
Canary sorts incoming mail with AI on every plan, so important messages rise to the top without rules. On Growth it drafts replies, rewrites, summarizes long threads and lets you search in plain English. Inbox triage runs on your device, and Canary doesn't use your email to train AI.
Verdict: Canary if you want the app to do the sorting and writing for you; Thunderbird if you'd rather build your own system with filters and tags.
Encryption and privacy
Both take privacy seriously, in different ways. Thunderbird has OpenPGP and S/MIME built in for free, and as an open-source project anyone can inspect its code. Canary blocks tracking pixels by default, and its Pro+ plan adds PGP plus SecureSend, which lets you send an encrypted message to someone who doesn't use PGP. More in our guide to PGP encryption.
Verdict: Thunderbird, for free encryption and open code. Canary if you need to send encrypted mail to people who've never set up PGP.
Platforms and mobile
Thunderbird runs on Windows, Mac and Linux, and Thunderbird for Android (which grew out of K-9 Mail) is on Google Play and F-Droid. An iPhone and iPad app, built from scratch, is available as an early public beta through TestFlight; it isn't on the App Store yet.
Canary runs on Mac, Windows, iPhone, iPad and Android, with one licence covering all of them. It doesn't run on Linux and has no web version.
Verdict: Canary if you use an iPhone or iPad. Thunderbird if you use Linux.
Microsoft 365 and Exchange
Both can add Outlook.com and Microsoft 365 accounts. Canary also connects to Exchange accounts directly. Thunderbird has recently added direct Microsoft Exchange and Microsoft 365 mail support, but Exchange calendars and contacts aren't supported yet.
Verdict: Close for mail. If you need Exchange calendars and contacts in the same app, check Thunderbird's progress first.
Thunderbird vs Outlook
Many people comparing Thunderbird are really choosing between it and Outlook. In short: Outlook is free on Windows but shows ads unless you pay for Microsoft 365, and it's the better choice for work calendars, Teams and shared mailboxes. Thunderbird has no ads, runs on Linux, supports add-ons and gives you PGP for free, but it isn't built around Microsoft 365. Our Canary Mail vs Outlook comparison covers Outlook in more detail.
Which should you choose?
- Choose Thunderbird if you want free and open source, use Linux, rely on add-ons, or want PGP without paying.
- Choose Canary Mail if you use an iPhone or iPad, want AI sorting and writing, or prefer a modern app that works the same on every device.
More comparisons: Apple Mail vs Thunderbird, Canary Mail vs eM Client and our list of the best free email clients.
Frequently asked questions
Is Canary Mail better than Thunderbird?
For iPhone and iPad users and anyone who wants AI help, Canary is the better fit. Thunderbird is better if you want free, open-source software, use Linux or depend on add-ons. (We make Canary.)
Is Thunderbird still free?
Yes. Thunderbird is free and open source, with no ads, and is funded by donations.
Is there Canary Mail for Linux?
No. Canary Mail runs on Mac, Windows, iPhone, iPad and Android. Thunderbird is one of the best email clients on Linux.
Is Canary Mail open source?
No. Canary Mail is a commercial app with a free plan. Thunderbird is open source.
Does Thunderbird have an iPhone app?
Not yet. Thunderbird for Android is available, and its iPhone and iPad app isn't on the App Store yet but is available as an early public beta through TestFlight, linked from Thunderbird's iOS roadmap.
Does Thunderbird have encryption?
Yes. OpenPGP and S/MIME are built in and free. Canary offers PGP and SecureSend on its Pro+ plan.
Is Thunderbird better than Outlook?
For a free, ad-free desktop app with add-ons and Linux support, yes. For Microsoft 365 work calendars, Teams and shared mailboxes, Outlook is better.