Other services provided are special incoming package handling, packaging, special deliveries/pickups, mail piece design for business and courtesy reply, and automated mail inserting machines. A customer may not deposit Global Express Guaranteed shipments weighing more than 10 oz or more than 1/2-inch in thickness and bearing only postage stamps as. All you need to do to mail the letter is. Mail for the USPS is also gathered and the necessary postage affixed for processing for 1st class letters and flats, packages, express mail, registered, certified, insured, and international mail. Calculate a Domestic or International Price to determine how much postage you will need when you ship a letter, card, large envelope, or package (limitations. The USPS provides different levels of package tracking for international packages depending on the mail class. In the U.S., there are USPS mailboxes you will see in most suburbs and cities. Mail Services is responsible for gathering, sorting, and delivering all interdepartmental campus mail and mail received from the United States Postal Service (USPS).