Wouldn't towns already have a postman by then?
Wouldn't someone have already thought of having some kind of mail carrier or messenger as a means of communication between the towns long before The Postman showed up? Most of the towns appeared fairly peaceful, and probably cooperated with each other for their survival. It seems to me that communication of this nature would have been among the first things the towns established.
I can guarantee Bethlehem had mounted messengers to carry orders to outposts or to civilian leaders in his territory, so why not the towns?