Exceptions from advertisement requirements

§ 6413. Exceptions from advertisement requirements Section 6412 does not apply to contracts for the transportation of mail— (a) by mail messengers under sections 6403 and 6423 of this title; (b) by highway post office service under sections 6351 to 6355 of this title; or (c) by steamships under sections 6405 and 6408 of this title.