USPS (United States Postal Service) is a national mail service that provides delivery services to individuals and businesses in the United States. While the exact policies can vary depending on the type of mail, destination, and specific circumstances, USPS typically operates on a reduced schedule on Christmas Eve, with most post offices closed. However, some locations may remain open for limited hours to accommodate urgent mail delivery needs. For specific information on USPS' delivery schedule and availability on Christmas Eve, it is recommended to contact your local post office or visit the USPS website for the most up-to-date information.