Comparison
Thunderbird vs Proton Mail
Thunderbird and Proton Mail are often compared, but they sit on different layers. Thunderbird is a free, open-source email client that connects to almost any provider. Proton Mail is an encrypted email service — a Swiss provider with its own apps. You can even use them together. Here's what actually differs.
Choose Thunderbird if
Choose Thunderbird if you want one free, open-source app to manage email from any provider — work, personal, your own domain, even Proton via Bridge (needs a paid Proton plan) — on your desktop, with calendar and add-ons.
Thunderbird Trust Report ›Choose Proton Mail if
Choose Proton Mail if you want the encrypted account itself: a Swiss provider with zero-access storage and end-to-end encryption between Proton users, delivered through its own private apps.
Proton Mail Trust Report ›| What it is | ||
| Type | Email client Bring your own provider | Email service Provider + apps |
| License | Open source MPL-2.0 | Apps open source Service proprietary |
| Maker | Mozilla | Proton AG Switzerland |
| Email & encryption | ||
| Works with any provider | Yes IMAP / POP | — Proton accounts |
| Built-in encryption | OpenPGP You set it up | End-to-end Default Proton-to-Proton |
| Zero-access storage | — Depends on provider | Yes Encrypted at rest |
| Practical | ||
| Calendar & contacts | Yes Built in | Separate apps Proton Calendar |
| Use them together | Yes via Proton Bridge (paid) | Yes via Proton Bridge (paid) |
| Price | Free | Free tier + paid plans |
The bottom line
Choose Thunderbird if
Choose Thunderbird if you want one free, open-source app to manage email from any provider — work, personal, your own domain, even Proton via Bridge (needs a paid Proton plan) — on your desktop, with calendar and add-ons.
Choose Proton Mail if
Choose Proton Mail if you want the encrypted account itself: a Swiss provider with zero-access storage and end-to-end encryption between Proton users, delivered through its own private apps.
Frequently asked questions
What is the difference between Thunderbird and Proton Mail?
Thunderbird and Proton Mail are often compared, but they sit on different layers. Thunderbird is a free, open-source email client that connects to almost any provider. Proton Mail is an encrypted email service — a Swiss provider with its own apps. You can even use them together. Here's what actually differs. In short: choose Thunderbird if choose Thunderbird if you want one free, open-source app to manage email from any provider — work, personal, your own domain, even Proton via Bridge (needs a paid Proton plan) — on your desktop, with calendar and add-ons. Choose Proton Mail if choose Proton Mail if you want the encrypted account itself: a Swiss provider with zero-access storage and end-to-end encryption between Proton users, delivered through its own private apps.
Is Thunderbird or Proton Mail cheaper?
At our last review, Thunderbird is listed at “Free · open source” and Proton Mail at “Free · Plus $3.99/mo”. Pricing is recorded as published by each developer and re-checked when the report is refreshed.
Which of Thunderbird and Proton Mail supports more platforms?
Thunderbird runs on Windows · macOS · Linux · Android. Proton Mail runs on macOS 12+ · Windows 10+ · Linux (Ubuntu 20.04+) · iOS 17.2+ · Android · Web.
Are Thunderbird and Proton Mail both safe to use?
Both carry an independent Altapp Trust Report. Thunderbird: 6/9 of nine checks verified, last full review Jul 19, 2026. Proton Mail: 8/9 of nine checks verified, last full review Jul 17, 2026. Each covers source verification, data and permissions, and known risks. Altapp publishes no score of its own — the count is a tally of what could be independently confirmed.