Erik Pevernagie said this quote
“ Postmen have a legendary aura. A ring at the doorbell may inflame a sense of expectation, suspense, secrecy, hazard or even intrigue. Ringing twice may imply a warning that trouble is on the way or an appeal to make the coast clear. Not all mailmen, though, will ring twice and await an eye-catching Lana Turner, whom they can whisper: With my brains and your looks, we could go places.” (The postman always rings twice) ”