Our home, built circa 1945, has a beautiful fireplace and mantle. Thanks to modern technology, it also has a functional gas insert, a welcome replacement to the wood-burning fireplace that inevitably filled our home with smoke. Over the 34 years we’ve lived in this house, we’ve frequently adorned the mantle with holiday decorations. But the most important decorations we hang on the mantle are those that come in the mail — annual holiday cards sent from family and friends.