Possibly. Sometimes delivery companies find it easier to just deliver them attempting to return to sender and dealing with headache of customer complaints since while it should have been clear to people buying the labels that they were not legit, a lot of people would be like "HOW WAS I SUPPOSED TO KNOW? I WANT MY MONEY BACK!"

Yes there is verification. Sometimes the label WAS valid but it was purchased with stolen credit card OR purchased then refunded after delivery to the client but before it entered the postal stream.

EDIT: Remember, boxes can be dropped off before someone processes them. Just hand them random postal carrier OR put them in postal pickup box.