Which document is referenced for information on mail transmitted in the United States?

The Domestic Mail Manual (DMM) is the central reference document for information related to mail transmitted within the United States. It provides detailed regulations, guidelines, and procedures that govern domestic mailing services. This includes information on mailing standards, rates, classes of mail, and applicable restrictions.

The DMM is essential for ensuring compliance with USPS policies, helping postal workers and customers understand how various types of mail can be processed and what requirements must be met for successful delivery. It serves as the definitive source of information for domestic mail, making it the most appropriate answer for this question.

In contrast, the other choices like the International Mail Guide focus on mail being sent to and from other countries, the Postal Service Handbook has broader operational guidelines that may not specifically pertain to domestic mailing, and the Shipping and Handling Regulations mostly concern the packaging and handling of items for shipping rather than detailed mailing processes.