For some reason I have it in the back of my mind that they were at one point accused of being a honeypot for US intelligence because of their association with MIT. Probably complete BS, but maybe not. Are they as open source as they claim to be? Looks like they’re on github. F-Droid seems to think they have some Google libraries or whatever that they use.
ProtonMail users, how do you like/dislike it?
I don’t have any proof, just a dim almost certainly wrong recollection in my aging brain.