Which of the following best describes the function of the DMM?

The function of the DMM, or Domestic Mail Manual, is primarily to govern domestic mail service regulations. It serves as a comprehensive guide that outlines the standards, regulations, and requirements for various mailing services within a country. This includes specifications on how to prepare and send mail, rates for different types of services, and operational guidelines that postal workers and businesses must follow when dealing with domestic mail.

While customer service guidelines, international mailing policies, and employment policies are important aspects of postal operations, they do not fall under the core function of the DMM. The DMM is specifically focused on domestic mail services, thus making the choice that identifies this function the most accurate representation of what the DMM is intended to achieve. Understanding the role of the DMM is crucial for anyone involved in mailing processes, as it ensures compliance and efficient handling of domestic mail.