One of the
most risky and expensive things USED to be sending a message or package
to someone in a distant city. That was before the use of portals to distant
places. The modern "post office" backroom usually is a grid of square portals
a few feet on a side through which your package is shoved. One can see
a person on the other side as if they are just in the other room, but in
reality they may be all the way in Trannor somewhere. The person on the
other side reads the address and decides which local portal there to shove
it into. This continues until your package is at the nearest town to your
destination, where it is either picked up there or delivered.