Which mail class typically requires a return receipt option?

The return receipt option is most commonly associated with Express Mail because this service is designed for items that require proof of delivery. When using Express Mail, senders can request a return receipt to verify that their package has reached its intended recipient. This is particularly important for urgent or valuable items, as it provides the sender with a documented confirmation of delivery.

In contrast, while other mail classes like Priority Mail and First-Class Mail do offer tracking services, they may not always include a return receipt as a standard feature. Standard Mail is typically used for bulk mailings and does not have the same level of service or tracking options as Express Mail. Thus, the efficiency and accountability of Express Mail coupled with the option of a return receipt make it clear why this mail class typically requires that option.