This is maddening. I called a local Mail-Boxes etc. type-place and asked them the question. They said they would ship whatever and weren't aware of FedEx and UPS policies...
Here's the problem with that. Numbnuts at the Mailbox Plus may actually ship it, but when it gets lost or stolen, or I should say "lost AND stolen", whoever the shipper is will deny your insurance claim.
It sounds terrible unfair (and it probably is) but you are charged with knowing all of the shipper's rules and regs (called "tariffs").