The most important factor with email, is that your inbox is encrypted at rest at all times... and cannot be bruteforced.

The chances of your email messages being 'man in the middled' are almost non-existent. Its a micro-percent of live investigations that does this.

The police RELY ON finding messages in either your inbox or the recipients. It doesnt matter if they are encrypted or not in reality. Of course they'd like to read them and if they are this deep into you. Its likely they still will (probably from the recipients lesser password hygiene than yours).

Almost no evidence is every 'plucked' out of the air and read. It just doesnt work that way.

However, software like Delta is better than nothing esp for normies. Its just limited in use for people who really need ways to frustrate LE.

Source: Ive been under NCA and FBI investigation before. Protonmail with the two password method stopped them every time. Memorise the 2nd password and password manager the first.