Hi. (´・ω・`)
In the mini-map window, the stop coverage of mail display is cut off by the passenger's coverage.
Check this image.

There are no mail treatment place other than the red company in the vicinity.
But somehow some coverage display are not square.
There is also a mail treatment place in the center of the town, but most of the coverage has been cut away and it seems as if it can not cover the city.
