Undeliverable-As-Addressed (UAA) —Mail that the USPS cannot deliver as addressed and must forward to the addressee, return to the sender, or send to a mail recovery center.

 

Unique ZIP Code —A ZIP Code assigned to a company, government agency, or entity with sufficient mail volume, based on average daily volume of letter-size mail received, availability of ZIP Code numbers in the postal area, and USPS cost-benefit analyses.

 

United States Code (USC) —The official restatement of the general and permanent laws of the United States; 39 USC contains laws relating to the USPS.

 

USPS Tracking —A service that provides the date and time of delivery or, if delivery was attempted but not successful, the date and time of the delivery attempt. This service may be obtained in two forms: (1) an electronic option for mailers who apply identifying barcodes to each piece, provide an electronic file, and retrieve delivery status information electronically; and (2) a retail option for mailers who retrieve delivery status through the USPS Internet at www.usps.com or by calling 800-222-1811.