How do I encrypt things?

[DireWolf]

^^^thanks for bumping this to remind me; had written up something last week during some in-flight down time, but ended up being way too much, so here's the condensed version:

Without taking any additional items/steps into consideration, mail sent from a ProtonMail account to a Gmail (or any other external/non-ProtonMail) address would only be encrypted while in-transit between mail-hosts (at best), and would still be stored in plain-text on the Google (or other provider) mail servers, fully available to them to access, mine/analyze, and/or disseminate your data within the sphere of those parties identified in the privacy policy (which is a damn large list).

ProtonMail uses OpenPGP to encrypt mailboxes and messages between ProtonMail users, with encryption/decryption through either the website, Mobile App, and/or ProtonMail Bridge (note that the messages retrieved through the Bridge are decrypted in local storage).

Also, they've exposed this functionality (and keyring management) to provide options for exchanging fully-encrypted email with external non-ProtonMail recipients - (e.g. Gmail, etc.); This allows for the message contents to be fully protected & unreadable even on remote servers (but watch out for those headers/subject-lines, which stay plaintext and are captured in any number of locations during message transit/processing).

All that's required for this is to simply create/associate a PGP Public Key with an address/contact, and PM will automatically encrypt all outbound email to that address (bidirectional encrypt/decrypt is seamless once Public Keys have been exchanged & verified; do not ever share a private key). Also, other than rules configured in a mail client, there is no native "auto-forwarding" capability in the PM service.

gpg4win is a good Windows/Outlook client bundle for creating and managing PGP Keyrings, and for "one-off's", PM has option for message encryption/expiration using OTPs.

Finally, be careful to (securely) store any keyrings & passphrases, or anything encrypted with such is toast should they be lost...