.....Mail delivery in large eastern cities......
I don't think that will ever happen in these large cities. In mine we have mail slots in the front door, or built into the front wall of the house and no room for mail boxes at the curb. In fact it would be illegal to do so. Apartments in brown stones have individual mail boxes with with keys in the vestibule. The mail person enters the vestibule via key that is placed in a post office box outside of the structure. Large apartments and condo's have mail rooms on the ground floor again with mail boxes with keys for each unit.
Where I live every house has a transom over the front door, and I have one over the back.. and in my bedroom, but I live in an old old neighborhood so that may not matter any more.