What is the difference between Fastmail and Proton Mail?

Fastmail: Paid, ad-free email hosting with calendars, contacts, custom domains and masked email addresses, built on open standards (IMAP, JMAP, CalDAV). Proton Mail: End-to-end encrypted email from Switzerland, bundled with Proton's calendar, drive, VPN and password manager.

When should I choose Fastmail?

An individual, family or small business wants fast, private email on its own domain without Google or Microsoft.

When should I choose Proton Mail?

Privacy is your first concern and you want encrypted email, especially between Proton users.

Fastmail vs Proton Mail

Fastmail and Proton Mail are both email server software. Fastmail is a commercial product from Fastmail Pty Ltd. Proton Mail is a commercial product from Proton AG.

Which to pick

Pick Fastmail when: An individual, family or small business wants fast, private email on its own domain without Google or Microsoft.
Pick Proton Mail when: Privacy is your first concern and you want encrypted email, especially between Proton users.

Side by side

Fastmail Proton Mail

What it does

Paid, ad-free email hosting with calendars, contacts, custom domains and masked email addresses, built on open standards (IMAP, JMAP, CalDAV).

End-to-end encrypted email from Switzerland, bundled with Proton's calendar, drive, VPN and password manager.

Watch out

No office suite or file storage included, and data is held in Australia and the US.

Desktop email clients need the paid Bridge app, and encryption limits server-side search and integrations.

Ready for

Production-ready (both)

Runs as

Cloud service and mobile app

Cloud service, desktop app and mobile app

Built with

Not published (both)

Source code

Closed source, sold by Fastmail Pty Ltd

Closed source, sold by Proton AG

What the license allows

Closed source: you use it under the maker's terms and cannot change or resell the code. (both)

How widely known

586 Wikipedia readers a month on phones

12k Wikipedia readers a month on phones

Other comparisons

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More email servers and webmail

Every email server product and project, ranked

Both sides were judged on 2026-11-03 from makers' descriptions, Wikipedia, READMEs and GitHub data. License, age and popularity lines are worked out directly.