Yes, the postal service delivers mail on Christmas Eve. The post office is open on Christmas Eve and it's possible to send and receive mail during this time. However, it's important to keep in mind that there may be delays or disruptions in service due to the holiday season, so it's always a good idea to plan ahead and mail your cards and packages early to ensure they arrive on time. Additionally, some post offices may have reduced hours or be closed on Christmas Eve, so it's always best to check with your local post office to confirm their schedule.