alt Hacker News> prides itself both on its end-to-end encryption
Their end-to-end encryption is pointless because the vast majority of any recipients will just leak the plaintext emails via their own account providers anyway. It only works under very specific circumstances (all parties are using it). I think their marketing overstates what their secure private email actually means.
Yes. If you send an email from a protonmail account to a gmail account that email is in google's system. Same if in the other direction. Would anyone using protonmail not know this. I would guess at least 99.9% of proton users understand this.