alt Hacker News> unless all parties are using proton, email is inherently insecure and somebody can/will have a record of your communication regardless.
That the person you're exchanging messages with, has your messages, is hardly a surprise. Not everyone-but-Proton sells your data though so it's not quite that black-and-white
You're not wrong, but I think it just means you can never be 100% safe, as even the recipient of your message may be secretly working against you.