Which OPNAVINST governs the conformity of letterhead envelopes and mailing labels?

The correct reference for the conformity of letterhead envelopes and mailing labels is OPNAVINST 5218.7B. This instruction provides guidelines and standards for the production and use of official Navy letterhead, including specifics on the arrangement, format, and appearance of envelopes and mailing labels to ensure consistency and professionalism in Navy correspondence.

Using this instruction helps maintain the Navy's image and ensures that all communications adhere to the established standards. This is important for both clarity and recognition of official documents. By referring to OPNAVINST 5218.7B, personnel can ensure they are compliant with the most current standards and practices set forth by the Navy regarding official correspondence materials.

Understanding which OPNAVINST is applicable is crucial for maintaining adherence to the Navy's communication standards, making option B the correct choice.