Yes, the post office does deliver on Christmas Eve, but it's a very busy day for them. They'll do their best to deliver all of the mail and packages that come in, but there may be some delays or missing items. It's always a good idea to check the tracking information for your package and plan accordingly. And if you're sending something that you really want to make sure is delivered on time, consider using a different delivery service, like FedEx or UPS.