Delivery attempt notices are left when no one is available to receive a delivery that requires a signature, payment of fees, or is too large to fit in the mailbox. A Delivery Receipt (PS Form 3849, "Sorry We Missed You") is left at the address showing that the mailpiece is being held at the addressee's local Post Office™.
A return date will also be written in the Final Notice section of the Delivery Receipt, if a second notice is delivered. The return date is the date your mailpiece will be returned to sender, unless you arrange for redelivery of your mail or pickup your mail at your local Post Office on or before this date.