USPS Priority Mail Express is a guaranteed way to send documents and packages to a destination overnight or in one to two days on any day of the year. If the US Postal Service doesn't deliver your package on time, they will refund the full postage cost. Packages under 70 pounds can be sent through Priority Mail Express to any address in the United States. Priority Mail Express comes with up to $200 in insurance and delivery tracking for free.
USPS is the only overnight shipping carrier that is allowed to deliver packages to a P.O. Box address. Other carriers, such as UPS and FedEx, cannot deliver packages to mailboxes in the Post Office.
USPS uses zone-based pricing for Priority Mail Express. There are nine zones in the United States. Prices are based on the distance from the original package location to the delivery destination. Prices start at $26.35 and up at the Post Office and $24.25 and up for Simpl Fulfillment clients. Additional fees apply for packages that must arrive on Sundays or holidays.