How to get a letter postmarked from the North Pole?

Yes, there is a Santa Claus

Greetings from the North Pole Post Office

And the Postal ServiceTM can help you prove it when Santa replies to your child’s letter — complete with the 99705 OFFICIAL North Pole Postmark!

Create the excitement of Christmas, letter writing, stamps and penmanship. Be sure to share your experience at #USPSNorthPolePostmark

Reference: usps.com