I was unhappy with the Outlook app built into Windows 11 and switched to the privacy-first email client Proton Mail. At first, I only used the free version of Proton Mail and Calendar, but I decided to upgrade to the rest of the Proton ecosystem with Drive, Docs, VPN, and Pass. I now have an unlimited subscription, which offers more storage in Proton Drive and additional features in the other apps.

Using Proton provides encryption and security benefits that Outlook simply can’t. I can encrypt emails via Outlook, but Proton keeps them safe while at rest. To be fair, Microsoft 365 users’ emails are encrypted in their inbox on Microsoft servers using AES encryption — the same encryption BitLocker uses. But I want more, and Proton has a zero-knowledge architecture, meaning emails and attachments are protected from malicious code, ad-targeting, and AI model training. So, I crossed the line into a more secure ecosystem with Proton Mail. I also decided to make it my default email on Windows 11 and all my devices.

4 Set Proton for Default MailTo links

Proton is primarily web-based, allowing you to set MailTo links as the default on Windows 11

You can’t set Proton Mail as the proper default handler on the Windows desktop like you can with Outlook. The app doesn’t register with Windows as a default mail handler. But there are some workarounds to consider, which make it easier to use as the default for web page email links.

The first time you open Proton Mail, a banner will display at the top asking you to set it as the default. Click on it, select the URL:MailTo Protocol option, select Proton Mail, and click the Set default button. If the message continues to appear, open the Proton Mail app, head to Settings -> All Settings -> Messages and composing, and uncheck the “Check your default mail application” switch.

Changing the default "MailTo:" handler directly from your browser is also possible. For instance, in a Chromium-based browser (Chrome, Brave, Edge), the first time you open Proton Mail, click the service handler icon in the address field and select Allow -> Done from the menu. In Firefox, navigate to the Proton Mail site, open Settings -> Make Proton Mail your default application, and click the Set as default button. Regardless of the process you use, once you're done, when you click a "MailTo:" email link, which is common on websites, Proton Mail will open.

3 Secure encryption

It offers proper end-to-end encryption of messages with a password

When you send an email message with Proton Mail, it uses the Transport Layer Security (TLS) encryption protocol, which protects your message while it’s being sent. It also uses proper end-to-end encryption while messages are at rest in your inbox. Since TLS is supported by most large email providers like Yahoo, Gmail, and Outlook, it allows you to send messages to users of those services from your Proton account.

Messages are always end-to-end encrypted by default when you send your message from Proton Mail to another Proton user. The other Proton user doesn’t need an encryption key. To send an end-to-end encrypted email from Proton to a non-Proton user, you must password-protect it, and the recipient can read it from a Proton environment via a link.

If someone emails you, it is encrypted with TLS in transit, unencrypted, and re-encrypted by Proton storage servers. It uses zero-access encryption, meaning even Proton staff can’t read it. So, whichever way you send or receive email messages, Proton has my back with secure encryption.

2 Features

Not as many as Outlook, and that’s a good thing

Outlook has more features and functionality, but that’s a good thing in my book. For instance, when I imported my Outlook Calendar to Proton, I wrote about it having unneeded features crammed into Calendar compared to Proton. With so much going on, it causes a claustrophobic experience.

But it has essential settings like mail forwarding, folder management, signature options, composing and theme management, filters, encryption keys, layout and color customization, IMAP/SMTP settings, and more. It also provides dark web monitoring, session management, and checks for authentication for Proton credentials, which are all included with a premium account.

The same is true for Outlook Mail, which has numerous features in the ribbon, most of which I don’t need, like Copilot. I'm very much against it and always remove Copilot from apps it's crept into. Proton includes exactly what I need for the task: sending and receiving messages and managing my inbox. It is a lightweight mail app, and using it is straightforward. But it includes features and settings that I occasionally use, making it the perfect app. However, if you need a ton of features, you might not like Proton's sparse landscape and prefer the Outlook app ribbon.

1 Cross-platform

I can set Proton Mail as the default on more than Windows

Whether I use Windows or my phone, I can set Proton as the default email app on my iPhone or Android. This is a benefit as it helps me move from the messages on Proton on my Windows 11 and my mobile devices. This is especially helpful while using Phone Link to connect my phone to Windows. On your iPhone, head to Settings -> Apps -> Proton Mail. Tap Proton Mail from the list. For example, I am changing the default email app from Gmail to Proton.

On Android, the process is a bit more convoluted but still straightforward. I’m using my Google Pixel 7a running Android 15 in this example. The options on your Android may vary, but this will give you an idea of what to look for. Head to Settings -> Apps -> Open default apps and tap Clear default preferences. Now, open Chrome, find a “MailTo” link, and tap it. When the option to select an app appears, choose Proton Mail and select Always. Once you follow the steps, Proton Mail will be the default email app on your Android phone.

Making Proton Mail the default instead of Outlook is beneficial

The above are why I make Proton Mail the default email client for all my devices. While you can’t make it your default through the Settings app on Windows 11, you can use a few workarounds, and there are good reasons to do it, namely, security.

I am happy with the encryption and zero-knowledge architecture the service provides for email. Proper end-to-end encryption is straightforward if you are emailing other Proton users, and password-protecting an email allows other users to open it from Proton servers. The recipient doesn’t even need to subscribe to an advanced Proton tier.

A free account provides them with 1 GB of storage, which is plenty for receiving encrypted emails. I feel safer using Proton instead of Outlook, since Microsoft can read your email content to target ads and train its Copilot AI. Knowing that even Proton staff can’t read my emails gives me peace of mind.