Encryption between protonmail accounts and when sending to non proton mail accounts: When you send an encrypted message to a non-ProtonMail user, they receive

Encryption between protonmail accounts and when sending to non proton mail accounts: When you send an encrypted message to a non-ProtonMail user, they receive a link which loads the encrypted message onto their browser, which they can decrypt using a passphrase that you have shared with them. You can also send unencrypted messages to Gmail, Yahoo, Outlook and others, just like regular email.