Once again, the Campus Post Office will offer a variety of letters that you can choose from and have sent to a child. “A Letter from Santa” will be forwarded to the Santa Claus Post Office in Indiana for a pictorial postmarking and then sent to the addressee on the envelope. View the available letters. Each letter costs $1.75. The last day to purchase a letter is Friday, Dec. 16. The Santa Claus Post Office is the only post office in the world with the Santa Claus name, and during the Christmas season, thousands of letters are mailed to Santa each year.