Which reference should be consulted for information on marking and handling classified correspondence?

The correct reference for information on marking and handling classified correspondence is DoDM 5200.01, Volume 2. This document specifically addresses the protection of classified information, including the standards and procedures for marking and handling such materials. It provides comprehensive guidance on how to ensure that classified information is handled securely, which is vital in maintaining the integrity of national security.

In contrast, the other references focus on different aspects of defense and communications processes. For instance, Volume 1 of DoDM 5200.01 primarily covers the overarching policies related to the safeguarding of classified information but does not delve into the specifics of handling correspondence. SECNAVINST 5216.5 pertains to Navy and Marine Corps correspondence management, focusing on the mechanics of writing and processing correspondence rather than the specifics of classified information management. The XO Manual typically includes operational procedures and responsibilities relevant to the executive officer's role, not specifically about classified correspondence handling.