2 Machinable and Automation Letters and Cards 2-1 Physical Standards for Machinable and Automation Letters and Cards 2-1.1 Basic Standards for Automation Letters and Cards Letters and cards claimed at any machinable, automation, or at USPS Marketing Mail carrier route price, must meet the standards in the DMM. Unless prepared as a folded self-mailer, booklet, or postcard, each machinable or automation letter must meet one of the following characteristics: Be a sealed envelope (the preferred method). If unenveloped, be sealed or glued completely along all four sides.