How Proton Mail messages are encrypted
All messages and attachments in your Proton Mail inbox are secured with zero-access encryption. That means nobody else can access your emails, not even Proton. Messages are encrypted in transit too, but the type of encryption depends on the recipient’s email provider.
In your inbox
All messages in your Proton Mail inbox are stored with zero-access encryption.
- Body content and attachments are stored with end-to-end encryption.
- Subject lines, recipient email addresses, and sender email addresses are encrypted, but not end-to-end encrypted.
This includes messages sent from non-Proton Mail addresses.
Sending and receiving messages
Between Proton Mail addresses
Messages in transit are always end-to-end encrypted.
From Proton Mail to non-Proton Mail addresses
Messages in transit are encrypted with TLS. Most third-party email providers support this.
Once the email reaches your recipient, it isn’t end-to-end encrypted by default. So the recipient’s email provider may be able to access it.
To send end-to-end encrypted messages to a non-Proton Mail address, use our password-protected emails feature.
From non-Proton Mail to Proton Mail addresses
Messages are encrypted with TLS in transit, then stored on our servers with zero-access encryption.
Unless the sender’s email provider uses end-to-end encryption, they may be able to retain a copy of messages sent from their side.
To receive end-to-end encrypted messages from a contact who doesn’t use Proton, you can:
- Send them a password-protected email and ask them to reply to it.
- Ask them to use PGP. How to export your Proton Mail PGP key
Alternatively, consider asking them to create a free Proton Mail email address, so your communications stay private by default.