Proton Mail AlternativesOnly Open Source apps categorised as Email Clients

The best open source Email Client alternative to Proton Mail is Tuta Mail. If that doesn't suit you, our users have ranked more than 50 alternatives to Proton Mail and eight of them are open source Email Clients so hopefully you can find a suitable replacement. Other interesting open source Email Client alternatives to Proton Mail are Posteo, Infomaniak kMail, Onion Mail and Criptext.

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Proton Mail alternatives are mainly Email Clients, but if you're looking for WebMail Providers or Calendar Apps you can filter on that. Other popular filters include Free, Self-Hosted and Open Source. These are just examples - use the filter bar below to find more specific alternatives to Proton Mail.
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Alternatives list

  1. Tuta Mail icon

    Tuta Mail

     531 likes

    Offers comprehensive encryption for email, calendar, and contacts with zero personal info required. Built on open source, install via Play Store, F-Droid, or APK, with Tor and VPN support. Both free and paid plans; utilizes quantum-resistant encryption ensuring privacy-focused, anonymous usage.

    103 Tuta Mail alternatives

    Cost / License

    Application types

    Platforms

    • Mac
    • Windows
    • Linux
    • Online
    • Android
    • iPhone
    • iPad
    • Flathub
    • F-Droid
    Tuta Mail screenshot 1
     
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    10
    Tuta Mail vs Proton Mail Comments
    Top Positive Comment
    Advik
    3

    Tutanota is end-to-end encrypted, as well offers 1 GB mail storage on free plan. The pro plans are cheap compared to protonmail, so it's better for low budget users

    Conner Vieira
    Positive
    -2

    Tutanota has historically been a lot more transparent, and arguably has been more honest about issues and plans

    Ada Byron
    Positive
    1

    I use both, ProtonMail is more secure but also more expensive and not as user-friendly. You cannot beat the price of Tutanota for service they provide.

    3 of 10 comments
    • Tuta Mail is Freemium and Open SourceProton Mail is also Freemium and Open Source
    • Tuta Mail is LightweightProton Mail is not according to our users
  2. Posteo icon

    Posteo

     85 likes

    Web- and IMAP-based email service. 4GB cost 1€/month. Information is hosted on encrypted hard drives. Electricity from renewable resources is used.

    73 Posteo alternatives

    Cost / License

    • Paid
    • Open Source

    Application types

    Platforms

    • Online
    Drag and drop
     
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    1
    Posteo vs Proton Mail Comments
    John Fastman
    Positive
    2

    Posteo could be a good Protonmail alternative. It offers email encryption in a similar way: Posteo's people, government surveillance and successful hackers won't get into your email content. It also offers a calendar feature, which protonmail users have been crying out for for years.

    • Posteo is Paid and Open SourceProton Mail is Freemium and Open Source
    • Posteo is Security-focusedProton Mail is not according to our users
  4. Infomaniak kMail icon

    Infomaniak kMail

     43 likes

    Privacy-focused Swiss email system provides 20 GB free storage, supports custom domains and unlimited storage, syncs contacts and calendars, is ad-free, and is part of a secure productivity suite used by over a million users across Europe on all devices.

    44 Infomaniak kMail alternatives

    Cost / License

    Application types

    Platforms

    • Online
    • Android
    • iPhone
    • Android Tablet
    • iPad
    • F-Droid
    Infomaniak kMail screenshot 1
     
  5. Ad
  6. Onion Mail icon

    Onion Mail

     5 likes

    The power of simplicity. Onion Mail can manage emails in the normal network and in the Tor. Onion Mail protect your privacy and anonymity.

    31 Onion Mail alternatives

    Cost / License

    • Freemium
    • Open Source

    Application types

    Platforms

    • Online
    • Android
     
  7. Criptext icon

    Criptext

     11 likes

    Finally, an email service that's built around your privacy. Get your @criptext.com email address and see what it's like to have peace of mind and privacy in every email you send.

    Cost / License

    • Free Personal
    • Open Source

    Application type

    Alerts

    • Discontinued

    Platforms

    • Mac
    • Windows
    • Linux
    • Android
    • iPhone
    Criptext screenshot 1
     
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    1
    Criptext vs Proton Mail Comments
    Guest
    Positive
    3

    Even thought Proton Mail is a good privacy focused email, it still holds both your emails and your keys on their servers. Regarding ownership, Criptext gives the user ownership over their keys, which reside only on the user's devices. It also uses Signal Protocol for encryption which I personally like better than just using pgp.

    Review by a new / low-activity user.
    • Criptext is Free Personal and Open SourceProton Mail is Freemium and Open Source
  8. Swisscows.email icon

    Swisscows.email

     5 likes

    Swisscows.email is another product of Swisscows AG. This product offers you secure email traffic. With Swisscows.email you can send your emails encrypted so that absolutely no one can read them. The service is comparable to a letter that is protected from prying eyes in an...

    Cost / License

    • Paid
    • Open Source

    Application types

    Platforms

    • Online
    • iPhone
    • iPad
    • Android
    • Android Tablet
    Swisscows.email screenshot 1
     
  10. Fripost icon

    Fripost

     6 likes

    Fripost – the Free Email Association. Fripost organize the people who want an alternative to "free" e-mail services where you are constantly under surveillance and personal data is handed over to third parties.

    Cost / License

    • Paid
    • Open Source

    Application types

    Platforms

    • Online
     
  11. Inboxer icon

    Inboxer

     3 likes

    Unofficial, free and open-source Google Inbox Desktop App. Built using electron, Inboxer includes a menu bar which is globalmenu compatible and works, and keyboard shortcuts.

    Cost / License

    • Free
    • Open Source (MIT)

    Application type

    Alerts

    • Discontinued

    Platforms

    • Mac
    • Windows
    • Linux
    Inboxer screenshot 1
     
8 of 8 Proton Mail alternatives