Stocking mail is a very special capability of moving messages, drawings and Christmas cards to Santa at the North Pole. But it is not always active. In fact, it is only activated when Santa says so. Santa has not yet activated stocking mail for this year.
According to the North Pole Radio News report above, which you can listen to by just clicking on it, Elf Hugo, who is the Post Master at the North Pole, says that it would be nothing but chaos for the North Pole Post Office if Santa activated it now.
It is a special technology that is held in reserve for when all other mail options no longer work at the North Pole.
So, please visit the North Pole Post Office online to see how you can get a message to Santa TODAY. If you want to use stocking mail, you will need to wait until Santa activates that service, which is usually not until around December 23rd or so.