It’s not E2E encrypted unless you’re using PGP or emailing another Proton user, which is basically nobody for most people. They do encrypt your email when it arrives in a way that is supposed to make them inaccessible to them (which is more than what most email providers do), so you’d need to trust that they’re not intercepting your emails and storing them somewhere unencrypted. Stuff like SimpleX/Cwtch/Signal is E2E encrypted though by default so their security is a lot better
It’s not E2E encrypted unless you’re using PGP or emailing another Proton user, which is basically nobody for most people. They do encrypt your email when it arrives in a way that is supposed to make them inaccessible to them (which is more than what most email providers do), so you’d need to trust that they’re not intercepting your emails and storing them somewhere unencrypted. Stuff like SimpleX/Cwtch/Signal is E2E encrypted though by default so their security is a lot better