I like the concept, even without any gesturing towards the supernatural. Being literally haunted by mail meant for the previous home owners, and then the slightly chilling realization that something big happened, that you'll never get the full story, and that your mail will continuously remind you of the gaps in what you know.
Not a big scare. Just a mundane small thing that might give you the heebie-jeebies when you're staring at the dark ceiling alone at night.