What is not a requirement for First-Class Mail International items?

In the context of First-Class Mail International, a sales receipt is not a requirement for mailing items. First-Class Mail International primarily focuses on sending letters and small parcels abroad with specific guidelines that ensure proper handling and delivery.

The key specifications for First-Class Mail International include ensuring proper packaging, which helps protect the contents during transit, maintaining a legible address to ensure the item reaches the correct destination, and often includes tracking capability, depending on the service chosen. While a sales receipt may be useful for tracking or record-keeping, it is not a mandatory requirement for all First-Class Mail International items, making it the correct choice in this scenario.