If you receive error 1101001, Must have exactly one CustomsInfo block, make sure your request includes the
If you encounter this error for an APO/FPO shipment, the shipment requires the
customs.customsInfo object because it has the potential to go outside the U.S., even though it uses domestic shipping services. USPS sets this requirement. For more information, see When does a domestic USPS shipment require a customs form?