A USPS tracking number can be found on a Post Office shipping receipt or sales receipt if insurance was purchased. The USPS website offers tracking services for packages and mail, along with options for setting up PO boxes or changing addresses. Customers can also receive tracking notifications through text messages and emails. If any issues arise, a customer service representative can be reached at 1-800-222-1811 to assist in locating the mail. Additionally, USPS offers various services such as Informed Delivery, purchasing stamps, and scheduling free package pickups.