39 U.S.C. § 5603 : Postal Service — Transportation Of Mail By Vessel — Transportation Of Mail — Transportation Of Mail By Vessel As Freight Or Express Date: 12 Jan 2017 TEXT PDF The Postal Service may require that mail be transported by freight or express when— (1) there is no competition on a water route and the rate or compensation asked is excessive; or (2) no proposal is received. A common carrier by water that fails or refuses to transport the mail when required to do so under this section shall be fined not more than $500 for each day of refusal. (Pub. L. 91–375, Aug. 12, 1970, 84 Stat. 773.)