I find it discouraging that it's almost 2018 and this function of E-mail has not been made standard in all clients yet.

I understand the concerns about trust, but why not make trust the extra step for now, and make encryption the standard. And in time we can standardize trust as well. (I know it's pretty standard already but I'm thinking about 'the average user')

"Well I can't trust the source so why bother with encryption" is what we have presently, and that's just ridiculous.