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, including Sundays and holidays. ... USPS is the only overnight shipping carrier that is allowed to deliver packages to a P.O. Box address.

How fast is priority mail overnight?

USPS Overnight, aka Priority Mail Express, offers guaranteed delivery in 1-2 business days. For Priority Mail International, delivery is guaranteed in 3-5 business days or your money back. The cost of this service depends on your package weight and delivery destination, primarily.

Is Priority Mail Express 1 day guaranteed?

Priority Mail Express is a guaranteed service. What does that mean? 1- and 2-day Delivery is guaranteed, which means that if the package is not delivered on time, you can apply for a refund. 1-Day Delivery guarantees delivery at 12:00 p.m. or 3:00 p.m. (destination time zone) the next day.