Very cool and unique idea. Liked using the mail throwing to kill enemies then able to pick it up again for delivering.
The world itself felt really big, but maybe because I mostly avoided vehicles due to not being able to throw mail from inside them.
Would have been cool to have the directional arrow remain on screen while pointing you to the nearest mailbox to help avoid getting lost.
Also would have liked the zoom controls mapped to the mouse wheel as that seems more natural in my head, but not sure how it feels in practice.
Really nice entry and cool concept to build upon.