I just don't know. I built that house on a smaller lot. Actually, I remember that there was a EA generated family lived there (they didn't exist in a fresh game). I deleted that family and demolished the house before building a new one. Can the mailbox still keep those unpaid bills of that family
After demolising the old house, I enter the lot and saw the mailbox and the ouside trashcan were moved to the sidewalk like TS2-style. Didn't it mean they were newly generated?