Emails sent between Proton Mail(new window) users are automatically end-to-end encrypted(new window) (E2EE). You can send a message that is automatically end-to-end encrypted to someone who doesn’t use Proton Mail if they use PGP(new window).
In addition to this, we offer a Password-protected Emails feature that allows you to send E2EE messages to any email user without the need for PGP.
With Password-protected Emails, your recipient receives an email telling them they have been sent a secure encrypted message. To read the message, they must enter a previously agreed-upon password. This takes them to a secure Proton Mail mailbox where they can read your message and respond using E2EE. You do not need a Proton Mail account to access this inbox.
How to use Password-protected Emails
1. Compose your email as usual. Any attachments will also be end-to-end encrypted. Before clicking Send, however, click the Encryption button (with the lock icon).
By default, Password-protected Emails will expire 28 days after they are sent. You can change this using the expiration timer(new window).
2. Choose a message password. Click Set when you are done (or tap Apply password if using our Android or iOS apps).
Your intended recipient will need the password to read the message, so make sure you share it with them. Ideally, you should do this using another secure communication channel (or tell them in person).
3. Back on the main composer screen, you will see the lock icon next to the recipient’s email address has turned blue to indicate the email is now end-to-end encrypted.
When you’re ready, click Send.
Recipients can reply to Password-protected Emails in a way that is also securely end-to-end encrypted (including attachments). However, they only reply to each email a total of five times.
Note that, due to technical constraints with end-to-end encryption, if you respond to a message sent by the recipient of a Password-protected Email, your response is not end-to-end encrypted by default and the entire message history will be sent unencrypted to the recipient.
To respond securely, you must re-enable Password-protected Emails, as described above. You can use the same password that you used for your previous emails or set a new one.