An APO address is a mailing address associated with U.S. Army or Air Force installations based overseas. APO stands for Army Post Office. U.S. Army soldiers and Air Force airman stationed overseas receive mail via their APO addresses.
Letters or packages sent to an APO address gets routed to distribution hubs in New York, California, and Florida before being sent overseas to an installation. The United States Postal Service handles all APO shipments. Packages larger than 108 inches in total circumference are not allowed, but package size and item restrictions vary for each installation. It is important to contact and verify with the service member you are sending a package to.