Holiday Mystery

We moved in to this house at the beginning of December in 2003, so it was reasonable that year that a lot of holiday cards were delivered that were not meant for us. Our postman has had this route a long time and I'm sure he redirected many such cards before we saw them but I still recall putting "no longer at this address - please forward to..." for the people we'd bought from or "return to sender" on the ones that were not for them (they only lived here two years or so). In the years since, we've only gotten one wrong card that I recall...but we get it every year. I remember it because the return address is a town I've never heard of otherwise (Vincennes?). The family to whom it's addressed hasn't lived here in at least twelve years, by our reckoning. We've been here three; the people we bought from two; the family before that, seven. The name on the mystery card doesn't belong to any of the people that we know have owned this house. Each year, I've marked the mystery card, "Addressee unknown - please return to sender" and each new holiday season, another card shows up. Thinking that whoever sends them gets no greeting in return makes me sad each year, so this year I've decided to mail the note back to the sender myself, enclosed in a note explaning that those people don't live here. I hope it's better for them to realize they're using the wrong address than to think they've been being ignored at the holidays year after year?