I had once lived in a very old house which needed a lot of work. Before I bought the house I met the owner who sat quietly in the living room.
After purchasing the house, I had the whole house repainted to give it a fresh look. The first week that I moved in and I opened the basement door, there was a big black cloud of ball spinning and I thought it was probably built up dust from the basement which was not logical but offered a good explanation.
About two months after living in the house, I heard footsteps coming from the basement to the first floor kitchen and when I looked around no one was there. So who can be making those footsteps I thought. I started cleaning the basement with all that I have because I wanted the house to look radiant. Under the basement steps, I saw a crufix attached to a bottle and I threw that out as well because I did not want so called rubbish under the stairs.
The second floor tenant complained that a boy who was about 15, the same age as her son was, watching her son on the computer while he was in the living room. The boy saw the young ghost for a few minutes he said.
The footsteps continued from the basement into my first floor apartment around midnight every night until I got tired of it. I finally said to it, "Stop walking in the kitchen so loudly every night. You are making a lot of noise and you are disturbing me from waking up to go to work." To my amazement, the walking in the kitchen stopped at midnight but I still heard the footsteps coming from the basement.
Eventually, the house was on fire and I sold it.
We do have federal laws regarding delivery, transference, opening, and tampering of mail, but that doesn't mean that every city and/or state enforce the laws just so. Further, each post office will have its own protocol, and I'm guessing that there's some sort of window on how many years the PO has jurisdiction over mail. (I'd google it but I'm lazy right now. It just makes sense.)
As a PI, I've had to deal with police dept's which insist they have no power over and/or funding for particular situations, so because of this, I have little doubt certain PO's, especially in small towns, are in a similar state.
It's really sad. I hate to see such wonderful history lost. But it happens. More often than people even realize, I'm sure.