When I was living in my first apartment after college, suddenly I started getting letters and phone calls from the electric company and two credit card companies stating that I hadn't paid my bills. I couln't remember even getting the bills, but chalked it up to a brain fart on my part and paid up. This went on for a couple more weeks - bills not arriving, some important paperwork for my student loans never arrived, etc.
I went down to the post office and complained. They said they would take a look into it. About a week later, I see and article in the newspaper about a letter carrier that got fired. Turns out he had stacks and stacks of undelivered mail in his basement. Seems he would deliver about half of his route, get tired, go home and take nap, and forget about the rest of the route.
Didn't have a problem with my mail after that!
Dave