鉄道郵便局
In March, 1873, Vail was assigned to duty in the office of the General Superintendent of Railway Mail Service, Washington, D.C. There he exercised special oversight of distribution of the mails, and justified to Congress the compensation the railways received for carrying the mail. In June, 1874, he was appointed Assistant Superintendent of Railway Mail Service. In 1875, he became Assistant General Superintendent.