A post office clerk or postal service clerk helps customers mail packages and letters, sorts and stamps mail, weighs items to determine appropriate postage amounts, and completes necessary forms for record-keeping. As a mail clerk with the postal service, your responsibilities include understanding and accurately calculating postage amounts, providing information to customers, managing the receiving and delivery of parcels, and organizing your workspace. You will sell stamps and other supplies, process customer payments, work with other staff to complete your daily duties, and maintain a friendly disposition when dealing with the public and your coworkers.