| >> Decryption is done in the browsers so it's not passing through the servers unencrypted. That cannot be for unencrypted emails, which is how most communications over email are going to be, because: 1. Most people or businesses are not on ProtonMail 2. Usage of PGP is nice, but very few people have published PGP keys 3. Opening a link to view a message is a big problem; personally I ignore such emails, can’t remember the last time that happened It also doesn’t work for unencrypted emails being sent to you, which are a majority. If I were to guess 99%+ of emails sent or received by ProtonMail customers are seen by ProtonMail’s servers in unencrypted form. And this is why ProtonMail is snake oil. |
Perhaps, rather than focusing on "most communications over email" (which don't involve ProtonMail's users whatsoever), it's more fair to ask whether ProtonMail enables encrypted communications with non-ProtonMail email users, and what threat models it is reasonably secure against.
You're right, though, that there are trade-offs to be made when it comes to using web-delivered JavaScript (although these problems need to be solved at the web platform layer [0], not unilaterally by a single service provider), and ProtonMail do not exactly advertise their security limitations (and nor do any other webmail providers).
[0] https://tools.ietf.org/html/draft-yasskin-http-origin-signed...