163e7687_Standards_for_Data_Stewardship__Category_I
[#] 4.2.4 [Action] Mailing documents via external mail carriers [Category-II] No special requirement [Category-III] No special requirement [Category-I] 
No classification marking on external envelope required; Confirmation of receipt is required as legally mandated.
Information Security Office - Minimum Security Standards for Data Stewardship
Category-I