What must customers provide for every item mailed?

Customers must provide an address for every item mailed because the address is essential for the delivery process. It ensures that postal services can accurately route the package to the intended recipient's location. The address includes crucial information such as the recipient's name, street address, city, state, and zip code, all of which are necessary to ensure the package reaches its proper destination.

Other options, while helpful or relevant in specific scenarios, do not meet the fundamental requirement for mailing an item. A return receipt is useful for confirmatory purposes but is not mandatory for all items. A tracking number aids in monitoring the package's journey, but it's provided after the item is processed. Weight is an important factor for calculating postage but is not something the customer would typically provide upfront when initiating the mailing process. Thus, the address remains the essential requirement for every item sent through the postal system.