Proton Mail AlternativesOnly apps categorised as Calendar Apps

The best Calendar alternative to Proton Mail is Tuta Mail, which is both free and Open Source. If that doesn't suit you, our users have ranked more than 100 alternatives to Proton Mail and 12 are Calendar Apps so hopefully you can find a suitable replacement. Other interesting Calendar App alternatives to Proton Mail are Posteo, mailbox, Mailfence and Fastmail.

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

More about Proton Mail

Proton Mail alternatives page was last updated Dec 19, 2025

Tuta Mail
558 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.
107 Tuta Mail alternatives
Cost / License
Freemium
Open Source (GPL-3.0)
Application types
WebMail Provider
Email Client
Origin
Germany
EU
Platforms
Mac
Windows
Linux
Online
Android
iPhone
iPad
Flathub
F-Droid
Android Tablet
Thunderbird
+1
Is Tuta Mail a good alternative to Proton Mail?

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10comments
Tuta Mail vs Proton Mail Comments

Top Positive Comment
Belsima
May 21, 2018
10
Functions on secure browsers like Klar and Tor.
Advik
Positive commentFeb 1, 2022
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 commentSep 13, 2021
-1
Tutanota has historically been a lot more transparent, and arguably has been more honest about issues and plans
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
Posteo
89 likes
Web- and IMAP-based email service. 4GB cost 1€/month. Information is hosted on encrypted hard drives. Electricity from renewable resources is used.
79 Posteo alternatives
Cost / License
Paid
Open Source
Application types
WebMail Provider
Email Client
Origin
Germany
EU
Platforms
Online
+9
Is Posteo a good alternative to Proton Mail?

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1comment
Posteo vs Proton Mail Comments

John Fastman
Positive commentApr 28, 2018
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
mailbox
76 likes
E-mail inbox, online office, cloud storage, and video conferencing. Business or personal plans. From 1 € /month (1.10 USD).
82 mailbox alternatives
Cost / License
Paid
Proprietary (AGPL-3.0)
Application types
WebMail Provider
Email Client
Origin
Germany
EU
Platforms
Online
+3
Is mailbox a good alternative to Proton Mail?

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1comment
mailbox vs Proton Mail Comments

John Fastman
Positive commentDec 24, 2016
2
Mailbox.org is a partial replacement for Protonmail. It offers a fully functional email solution (email, calendar, contacts), but with the added benefits of PGP encryption support (you can handle the keys or let them do it). It also allows you to send links to people who don't use PGP if you want to send private messages. For the encryption, it's a bit like Protonmail. For everything else, it's like a privacy-respecing Gmail alternative.
mailbox is Paid and ProprietaryProton Mail is Freemium and Open Source
mailbox is Security-focusedProton Mail is not according to our users
Ad
Fastmail
Fastmail offers secure email hosting with comprehensive webmail services, including IMAP, POP, and SMTP protocols. It supports file sharing, shared folders, large mailboxes, instant messaging, and is compatible with popular email...

https://www.fastmail.com
Learn More
Mailfence
65 likes
This secure email platform offers end-to-end encryption, a comprehensive suite with Calendar and Documents. Mailfence is inter-operable with OpenPGP services, features digital signatures, provides keystores, and available as a PWA for mobile independence while ensuring no ads, trackers, or surveillance.
72 Mailfence alternatives
Cost / License
Freemium
Proprietary
Application types
WebMail Provider
Email Client
Origin
Belgium
EU
Platforms
Online
Android
iPhone
Android Tablet
iPad
+9
Is Mailfence a good alternative to Proton Mail?

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7comments
Mailfence vs Proton Mail Comments

Top Positive Comment
PhmNguynHngThnh
Oct 1, 2019
5
Mailfence offers more functionality than Proton mail with Calendar, Document, Chat, and Group functionality. Moreover, the price is much lower than other competitors.
Top Negative Comment
Guest
Aug 29, 2020
2
Costs money to use with 3rd party programs.
Review by a new / low-activity user.
Guest
Positive commentMar 15, 2020
1
because its free and don't need any pay and don't want phone number to sign in
Review by a new / low-activity user.
3 of 7 comments
Mailfence is Freemium and ProprietaryProton Mail is Freemium and Open Source
Fastmail
78 likes
Fastmail offers secure email hosting with comprehensive webmail services, including IMAP, POP, and SMTP protocols. It supports file sharing, shared folders, large mailboxes, instant messaging, and is compatible with popular email programs. Excellent for businesses with compliance features.
75 Fastmail alternatives
Cost / License
Paid
Proprietary
Application types
WebMail Provider
Mail Server
Origin
Australia
Platforms
Mac
Windows
Linux
Online
Android
iPhone
Android Tablet
iPad
Flathub
Flatpak
+6
Is Fastmail a good alternative to Proton Mail?
Infomaniak kMail
47 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.
49 Infomaniak kMail alternatives
Cost / License
Freemium
Open Source (GPL-3.0)
Application types
WebMail Provider
Email Client
Origin
Switzerland
Platforms
Online
Android
iPhone
Android Tablet
iPad
F-Droid
+8
Is Infomaniak kMail a good alternative to Proton Mail?
Vivaldi Mail
34 likes
Vivaldi Mail is a free email service with no ads and no strings attached developed by Vivaldi Technologies. It also offers contacts and calendar features, search capabilities, folders management, WEB/POP/IMAP access, 10GB of storage capacity, 20 MB of maximum attachment size...
103 Vivaldi Mail alternatives
Cost / License
Free
Proprietary
Application types
WebMail Provider
Email Client
Origin
Norway
Platforms
Online
Vivaldi
+2
Is Vivaldi Mail a good alternative to Proton Mail?

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1comment
Vivaldi Mail vs Proton Mail Comments

John Fastman
Positive commentApr 28, 2018
0
Vivaldi mail offers PGP-based email encryption, similar to Protonmail. But the web client is much less well developed. However, unlike Protonmail (at the time of writing), they allow you to import your own PGP keys, which is nice (a feature Protonmail users have been demanding for years).
Vivaldi Mail is Free and ProprietaryProton Mail is Freemium and Open Source
Mailo
25 likes
The mail service which respects you.
Cost / License
Freemium
Proprietary
Application types
WebMail Provider
Email Client
Origin
France
EU
Platforms
Online
Android
iPhone
Android Tablet
iPad
OpenPGP
+3
Is Mailo a good alternative to Proton Mail?
Kolab Now
43 likes
Kolab Now provides a suite of intuitive apps in a user friendly environment to make your day to day online comms easier, smarter and most importantly; secure.
Cost / License
Paid
Open Source
Application types
WebMail Provider
Mail Server
Origin
Switzerland
Platforms
Online
Software as a Service (SaaS)
DAVx5
Is Kolab Now a good alternative to Proton Mail?
Mailture
Like
Mailture, a secure, business-oriented email service, is made to cater to all your emailing needs. With top-notch collaboration and communication features, Mailture offers much more than your usual inbox.
Cost / License
Paid
Proprietary
Application types
WebMail Provider
Email Client
Origin
United Kingdom
Alerts
Discontinued
Platforms
Software as a Service (SaaS)
Is Mailture a good alternative to Proton Mail?
mail2world
3 likes
the free email that has everyone talking!.
74 mail2world alternatives
Cost / License
Freemium
Proprietary
Application types
WebMail Provider
Calendar
Origin
United States
Platforms
Online
Is mail2world a good alternative to Proton Mail?
VFEmail
6 likes
Free email with privacy and security.
Cost / License
Freemium
Proprietary
Application types
WebMail Provider
Calendar
Platforms
Online
Is VFEmail a good alternative to Proton Mail?

12 of 12 Proton Mail alternatives

Proton Mail AlternativesOnly apps categorised as Calendar Apps

Alternatives list

Tuta Mail

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Posteo

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mailbox

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mailbox vs Proton Mail Comments

Mailfence

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Fastmail

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Infomaniak kMail

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Vivaldi Mail

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Mailo

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Kolab Now

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Mailture

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mail2world

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VFEmail

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