However, if you think someone in the system is stealing your mail file a complaint.
Yep that works. I know they steal gift cards, cheeks or cash, because they never get there, most of the time the cards get there minus the gift. I have seen videos of the loyal employees you speak of opening the cards.
If I really want something to arrive I have to pony up for insured or special delivery.
I avoid the problem entirely by using FedEx or UPS. There was a time that the iceman or milkman or postman could deliver anything because the doors were unlocked, that is a long gone era.