So, just curious, how does filtering out spam work, if the email provider does not have access to the contents? Not saying it's not possible, but I wonder if any current users of ProtonMail could comment on this? If you use ProtonMail, are you mostly just on your own in regards to spam filtering?
This is for external mail only though. Presumably they don't have a bad problem with internal users sending mail to other internal users. I'm guessing any that did would get found quickly via reporting or heuristics.