District of Columbia Code Division I. Government of District. § 2-702. Permitted categories of official mail.

(1) A request for the matter, article, material, or document has been previously received by the agency;

(2) The mailing of the document is required by law;

(3) The material or matter requests information pertinent to the conduct of the official business of the agency;

(4) The material contains information relating to the activities of the agency or to the availability of agency publications or other documents;

(5) The enclosures are forms, blanks, cards, or other documents necessary or beneficial to the administration of the agency;

(6) The materials are copies of federal, state or local laws, rules, regulations, orders, instructions, or interpretations thereto; or

(7) The materials are being mailed to federal, state, or other public authorities.