39 C.F.R. § 263.2 Policy.
Title 39 - Postal Service
It is the policy of the U.S. Postal Service to establish and maintain schedules specifying the retention periods required for all official and duplicate record copies. Furthermore, it is the policy that all duplicate record copies and non-record material will be disposed of as soon as they have served their purpose.
Title 39: Postal Service
PART 263—RECORDS RETENTION AND DISPOSITION
§ 263.2 Policy.

