Mail does not run on the day after Christmas in the United States, as it is a federal holiday. However, some mail may be delivered if it is deemed necessary for business or public safety reasons. Many people also use this day as an opportunity to catch up on missed correspondence and to send out last-minute gifts or cards to loved ones. If you have a package or letter that needs to be sent urgently, you can contact your local post office to see if they offer any special services or if there are any alternative delivery options available.