Is Proton Mail encrypted?
Yes. Only you and the people you write to can read mail between Proton users, and only you can read your stored mail. Subject lines aren't sealed, and mail to other services isn't sealed unless you add a password or the person uses PGP.
Checked on 25 October 2026 against 7 sources.
Made by Secria, which makes Secria Mail. We grade every app by the same rules, our own included. How we check
- Between its own usersOnly you and the people you write toProton says mail between Proton addresses is always end-to-end encrypted, but subject lines are not.1
- To other servicesPartlyProton briefly handles mail to and from other services in readable form before sealing your copy, and the other service can read its copy unless you add a password or the person uses PGP.1, 2, 3, 4, 5
- Stored mailboxOnly youBodies and attachments are stored with zero-access encryption, including mail from other services, while subject lines, senders and recipients stay readable to Proton.1, 3
- Post-quantumYes, once you turn it onProton has offered opt-in post-quantum keys for new encrypted mail on all plans since May 2026, rolling out gradually, and older mail isn't re-encrypted yet.6, 7Turn it on
- Who holds the keys
- You. Proton says your mail is locked with a private key that only you control, so it can't decrypt your stored messages and attachments.
- What Proton can still see
- Sender and recipient addresses, subject lines, attachment names, the IP address incoming mail came from, when messages were sent and received, and mail to or from other services for a moment before it's sealed.
Turn on post-quantum keys, once
- Sign in at account.proton.me and open your account settings.
- Select Encryption and keys in the sidebar.
- Under Post-quantum protection, click Enable post-quantum protection.
- Check the box, click Enable and generate keys, then enter your password.
Proton is still rolling this out, so the option may not show yet. It protects new mail from then on, not mail already in your mailbox, and it pauses end-to-end encrypted forwarding if you use it.
Can Proton read my email?
Not the messages or attachments once they're stored. Proton says all messages in your mailbox are stored with zero-access encryption, including mail from other services1. Its privacy policy says it can't scan mail after it has been encrypted3.
Proton can see some details. Its privacy policy lists sender and recipient addresses, subject lines, attachment names and send and receive times3. Mail arriving from other services is scanned for spam in memory before it is encrypted3.
Is Proton Mail end-to-end encrypted when I email Gmail users?
Not by default. Proton's help says mail to other providers is protected with TLS on the way, and the recipient's provider may be able to read it1. Mail coming in from a service like Gmail is readable to Proton for a moment, then sealed with your key2.
On all plans, including free, you can seal a message to anyone with a password-protected email: click the lock icon while you write, set a password, and share it with the person another way4. These messages expire after 28 days at most4. Proton also seals mail automatically to people on other services who publish a PGP key it can find5.
Are Proton Mail subject lines encrypted?
Not end to end. Proton says it follows the OpenPGP standard, where the subject line sits in a header that isn't end-to-end encrypted1. Its privacy policy lists the subject among the details it can access3.
Is Proton Mail post-quantum?
Only if you turn it on. On 5 May 2026 Proton announced post-quantum protection for Proton Mail on all plans, including free, rolling out gradually6. Once you turn it on, your account starts using new keys meant to protect future encrypted emails7.
It doesn't re-encrypt mail already in your mailbox yet, though Proton says it plans to6, 7. If you use end-to-end encrypted forwarding, turning it on pauses that7.
How Proton Mail compares
Sorted by how many parts are sealed by default, then by how many can be. Ties go A to Z.
Sources
- How Proton Mail messages are encrypted, Proton. Read on 25 Oct 2026.
- What is zero-access encryption?, Proton. Read on 25 Oct 2026.
- Proton Mail Privacy Policy (last modified 14 September 2026), Proton. Read on 25 Oct 2026.
- Password-protected emails, Proton. Read on 25 Oct 2026.
- How Safe is Proton Mail? Security Features Explained, Proton. Read on 25 Oct 2026.
- Proton Mail now supports post-quantum encryption (5 May 2026), Proton. Read on 25 Oct 2026.
- How to enable post-quantum protection in Proton Mail, Proton. Read on 25 Oct 2026.
Changes to this answer
- First published.