Mailbox is a cheerful object of his namesake who speaks with a thick New York accent. Mailbox normally sits on a post at the Blue's Clues house's front pathway. When he has a letter for Steve, Joe, or Josh, he uses an extension arm (which he invented himself) to enter through the living room window. His extension arm is impractically long and can transport him anywhere.
Mailbox's favorite hobbies are delivering letters, and telling jokes. He likes to make others laugh and wants to become a comedian when he grows up. In almost every episode, Steve, Joe or Josh sing a special song before Mailbox delivers a letter or incoming e-mail. On some rare occasions, such as in "Blue's Big Pajama Party," Mailbox makes a special nighttime mail delivery. Mailbox has received letters for himself in Mailbox’s Birthday, The Wrong Shirt, Blue’s Big Costume Parade, and Mailtime Mystery. In Joe's Clues, Mailbox gave a letter to Blue, and in Playdates, Mailbox and the Viewer gave Joe his letter together and even sung Mailtime together as well.
Since Mailbox lives in front of the Blue's Clues house, he is usually the first person to greet visitors. In the first four seasons, Mailbox is also the first character to appear in each episode. When the opening sequence begins, he is seen smiling and swaying back and forth on his post, as kind of a silent greeting to the viewers.
In the original series, Mailbox was voiced by Michael Rubin for its entire run. Rubin was one of the show's two music composers, alongside Nick Balaban (who voiced Mr. Salt). Rubin was always credited under the stage name "Seth O'Hickory". In the reboot, he is voiced by Canadian voice actor Doug Murray.
