[iggldiggl]

> that makes filtering impossible

... including spam filtering, which matters somewhat for consumers, too.

Then there's the issue of search - with webmail you have no realistic choice but to rely on server-side search, and the same issue likely applies on phones even when using a dedicated mail app. (And indeed ProtonMail currently only offers meta-data search, but no full text body search)

[AmericanChopper]

I didn’t specifically say spam filtering, because there’s technically lots of spam filtering you can do with only metadata. But yeah you’re right, any form of server side content filtering (including search) would be impossible.