With the USPS's Signature Confirmation, you (or your customers) can access
information on the Internet about the delivery status of First-Class Mail
parcels, Priority Mail and Package Services (Standard Post, Media Mail, and
Library Mail), including the date, time, and ZIP Code of delivery, as well as
attempted deliveries, forwarding, and returns. Signature Confirmation service is
not available to APO/FPO addresses, foreign countries, or most U.S.