are zip codes required
The nine-digit ZIP code is required for all classes of mail. The ALNAV message is available at http://www.public.navy.mil/bupers-npc/reference/messages/Documents/ALNAVS/ALN2013/ALN13047.txt. ZIP codes are a system of postal codes used by the United States Postal Service (USPS) since 1963. The term ZIP is an acronym for Zone Improvement Plan. All U.S. addresses have a standard five-digit ZIP code that informs the postal service of the area of the country and the post office where mail is received. In 1983, the USPS added four digits to ZIP codes to help further pinpoint a recipient's location.