In the fall of 1868, he was made operator and afterward agent at Pine Bluffs, Wyoming, on the Union Pacific Railroad.

[4] In Spring 1869, Vail was appointed clerk of the railway mail service between Omaha, Nebraska, and Ogden, Utah.

[4] He was promoted to the Chicago and Iowa City railway post office, an important distribution point at the time.

Postal employees under general civil service laws and established a system of six months' probationary appointments, which were subsequently adopted by all agencies.

Vail became convinced as a result of his association with Hubbard that the telephone would eventually revolutionize world communication, and he became a vigorous, though generally unsuccessful, promoter of Bell stock.

[5] Hubbard was impressed with Vail and offered him the position of general manager of the American Bell Telephone Company in 1878.

They had one son, Davis Righter Vail (July 18, 1870 – December 20, 1906),[4] who died after a 10-day bout with typhoid fever in 1906.

[4] In 1890, he received a concession from the federal government of Argentina to build a generating station at Cordoba to supply power to a trolley system in Buenos Aires.

[3] As a tribute to Vail, telephone service across the United States was halted for one minute on the morning of April 18, 1920, while his funeral was conducted in Parsippany, New Jersey.

Vail acquired the scientific book collection of George Edward Dering in 1911 and presented it to the library of Massachusetts Institute of Technology.