Thank-you cards—heartfelt expressions of gratitude for gifts, services and general kindness— seem to be rare in an age when the Internet continues to reduce human interaction. Although our society has changed greatly over the past century, the etiquette(礼节) of thank-you notes has not. While most people would agree that thank-you notes under these circumstances are a necessity, there are still those who forever postpone or are forgetful for unknown reasons. And at no time of the year are thank-you notes more visible than June, the month of brides and graduations, and the beginning of summer parties. "It’’s a must-do thing. A real thank you does not come by e-mail. They come in the mail in an envelope. And what comes out of an envelope is a beautiful thing to touch and to handle and to pass around. for everyone to read," said etiquette expert Letitia Baldrige. Don’’t think for a second that Baldrige is old-fashioned. Handwritten thank-you notes—any handwritten correspondence, for that matter — have taken on an air of extra importance and dignity in this e-hyper world. Baldrige remains hopeful that the art may be enjoying a renaissance(复兴). More than simply obeying rules of etiquette, thank-you cards are a sign of caring. "They’’re more important now than ever," expert Peter Post says. "You’’re building a relationship. And part of building that relationship is that you acknowledge when someone has done something nice for you." The payoff(回报), Post says, can be huge. "It will continue indefinitely," he says. "The more we do it, the more it comes back to us, and it’’s a benefit to us all. It makes our world a little bit nicer place to live in. " By saying "at no time of the year are thank-you notes more visible than June" the writer means___________.