LOVELAND, Colo. – Love is in the air … and the mail … in the northern Colorado city of Loveland. Every year, tens of thousands of people from around the world route their Valentine’s Day cards to the “Sweetheart City” to get a special inscription and the coveted Loveland postmark. The re-mailing tradition has been going on for nearly 80 years and is the largest of its kind in the world, according to Mindy McCloughan, president and CEO of the Loveland Chamber of Commerce.