Correspondence of the members of the diplomatic corps of the countries of the Postal Union of the Americas and Spain stationed in the United States may be reciprocally transmitted in the domestic mails free of postage, and be entitled to free registration without right to indemnity in case of loss. The same privilege is accorded consuls and vice consuls when they are discharging the function of consuls of countries stationed in the United States, for official correspondence among themselves, and with the Government of the United States.
Structure US Code
CHAPTER 32— PENALTY AND FRANKED MAIL
§ 3203. Endorsements on penalty covers
§ 3204. Restrictions on use of penalty mail
§ 3205. Accounting for penalty covers
§ 3206. Reimbursement for penalty mail service
§ 3207. Limit of weight of penalty mail; postage on overweight matter
§ 3208. Shipment by most economical means
§ 3209. Executive departments to supply information
§ 3212. Congressional Record under frank of Members of Congress
§ 3213. Seeds and reports from Department of Agriculture
§ 3214. Mailing privilege of former President; surviving spouse of former President
§ 3215. Lending or permitting use of frank unlawful
§ 3216. Reimbursement for franked mailings
§ 3218. Franked mail for survivors of Members of Congress
§ 3220. Use of official mail in the location and recovery of missing children