Of course you know that it must go through an FFL at the receivers end, if shipping out of state. (I presume you are not shiping it to yourself). This is a Federal law and some state laws may be more restrictive.
Some drop ship locations such as Mailboxes Etc will not accept a firearm for shipping due to their internal policies. I have found it easiest if you take the gun to a "Hub" or main drop off location for the big shippers (UPS/FedEx)
The former Mailboxes USA chain of franchises is now owned (the parent company, from whom the individual stores license the right to operate) 100 percent by UPS, so they ARE a part of UPS. And it is UPS policy that they are not allowed to accept shipments of firearms or ammunition at those stores. Only at UPS hubs.
Ah, okay. I was speaki,g from my experience at a ups outlet store. The lady looked at me like I was a criminal and had no clue about how to ship a rifle. I was just there to get a box, not ship it.
UPS bought the parent company. Each location is an independently owned location - just like McD's. There are corporate policies that are implemented and as a franchisee, you will follow.
As you stated, it is their POLICY, it is NOT illegal, just SOP for them, whereas MY local Fedex and USPS both have ZERO issues and Fedex's rates in my area seem to be less than UPS