Comment by kachapopopow

this is a soft case of "you're using it wrong/didn't read what proton mail is" they physically cannot offer you this functionality even if they really wanted to. Although you can enable message body search and it has to be indexed on your client (which takes a long time and is a pretty bad UX - but there is no alternative).

Instead (and this is the suggested way) you can link it to an email client which stores emails on device unencrypted using proton mail bridge. They could pre-load all content in your browser, but again it's pretty bad UX and you would sit there wondering why the search takes 1-2 minutes on a fresh window session if it was on "by default". You *can* use automatic tagging for assisted search (like "if contains flight, add flight tag") though if you want to continue exclusively using the web app(s).

But there is a pretty valid concern here: why don't the native iOS and android apps have an email index?! I guess they don't want to be caught "storing" your emails unencrypted? I don't know - should really be an option.