I’ve moved most active and new accounts over to Proton, and I’d like to migrate all my old emails too, but before that I’ll need to be able to search mail content from mobile.
This article covers the topic for desktop: https://proton.me/support/search
I hardly ever use search or mail on desktop though - it’s usually on the go I’m looking for information.
When is this coming to mobile apps?
Building a local encrypted index of the contents of the email is probably what’s taking them time to build. Remember encryption. Can’t be done server side.