Every railroad corporation shall, upon request of the postmaster general or of an authorized agent of the post office department, carry the mails at such times and upon such trains as may be desired by him upon the terms provided in the two following sections.
Mass. Gen. Laws ch. 160, § 201
Required upon request
Official source: Massachusetts Legislature. Reproduced from public-domain Massachusetts statutes; confirm against the official source for the current text. Not legal advice.