Sending annual Christmas cards to friends and family is a time-honored Christmas custom for many people who celebrate the holiday. "There's nothing more uplifting than opening something other than bills in the mailbox," etiquette expert Jacqueline Whitmore explains. "Christmas cards may also evoke a sense of nostalgia, and I believe that after an isolating couple of years, people are yearning for that kind of festive connection." When it comes to sending Christmas cards, Whitmore advises sending them as soon as possible, especially considering USPS postal service delays that began in October.