The post office is a private business, BUT it follows fedral regulations and federal laws. It is considered a federal building.Because of that, it has to follow federal rules. Unless you are LEO you are not allowed to carry in any PO. If its in a mall, you are fine until you step through the door of the PO. If anyone wants to carry in a PO, you go right ahead. I certainly will not. By the way, my uncle was a regional district manager for over 30 yearsand several other family members also work at other facilites. I might have a little insight.
Glock 23 / 33
Kimber Pro Carry SLE
S&W 1911ES, S&W 6906, S&W M&P 9