United States Statutes at Large/Volume 1/5th Congress/2nd Session/Chapter 56
Be it enacted by the Senate and House of Representatives of the United States of America in Congress assembled, Act of March 2, 1799, ch. 43, sec. 17.That all letters and packets to or from the Secretary of the Navy, shall be received and conveyed by post, free of postage, under the like restrictions and limitations as are provided respecting letters and packets to or from the heads of the other departments of the government, by the nineteenth section of the act, entitled 1794, ch. 23.“An act to establish the post-office and post roads within the United States.”
Approved, June 22, 1798.