What processes letters and packages that are incoming and outgoing for military installations?

The Official Mail Center is responsible for processing letters and packages that are incoming and outgoing for military installations. This center handles all official communications and ensures that mail is sorted, distributed, and delivered efficiently throughout the military network. It plays a critical role in managing the flow of official correspondence, which is essential for maintaining communication and operational effectiveness within military installations.

While other options involve mail handling, they serve different specific purposes. Military Post Offices typically focus on providing postal services to military personnel and their families, Aerial Mail Terminals deal primarily with mail transported by air, and Military Mail Terminals handle mail designated for military use but may not encompass the full range of official correspondence managed by the Official Mail Center. Understanding the specific roles of these different entities clarifies why the Official Mail Center is the correct choice for this question.