As someone who has read plenty of discussions about email security (some of them in this very community), including all kind of stuff (from the company groupie to tinfoil-hat conspiracy theories), I have decided to put ~~too many hours~~ some time to discuss the different threat models for email setups, including the basic most people have, the "secure email provider" one (e.g., Protonmail) and the "I use ~~arch~~ PGP manually BTW".
Jokes aside, I hope that it provides an overview comprehensive and - I don't want to say objective, but at least rational - enough so that everyone can draw their own conclusion, while also showing how certain "radical" arguments that I have seen in the past are relatively shortsighted.
The tl;dr is that email is generally not a great solution when talking about security. Depending on your risk profile, using a secure email provider may be the best compromise between realistic security and usability, while if you really have serious security needs, you probably shouldn't use emails, but if you do then a custom setup is your best choice.
Cheers
I suppose, but is there any documented occurrence of that? It seems like a whole stack of what-if scenarios required for that to happen. At that point you should be more concerned with someone beating your password out of you.
Not that I know, which is the reason why I essentially didn't consider those threats relevant for my personal threat model. However, it's also possible it happened and it was never discovered. The point is that there are risks associated with having the same provider having access to both the emails (and the operations around them) and the keys/crypto operations.
If I were a Snowden-level person, I would probably consider that though, as it's possible that the US government would try to coerce -say- Proton in serving bad JS code to user X. For most people I argue these are theoretical attacks that do not pose concrete risk.