The first telephone line in Warren was established between the Keeling Lumber Co. sawmill and the C.P.R. station in 1904. In 1911, a telephone line was installed between St. Charles, Warren and Cache Bay, with approximately 35 subscribers. The line between Warren and Cache Bay was abandoned in 1917. The same year, the Dunnet Municipal Telephone Company was organized under the Telephone Act, administered under the Ontario Railway and Municipal Board. The first exchange was located in a house at 3 Dyke Street in Warren.
The first listing of Warren, Ontario in the Bell Canada directories was in 1910. Bell's first telephone office in Warren was announced in 1911, and the Dunnet Municipal Telephone System appeared in the Bell directories in 1917.
The village of Markstay was fully serviced by telephones by 1959.
The mail for the Warren area was initially carried from Noelville and Monetville to St. Charles and Warren. The mail carrier would travel the 26 miles one day and return the following day. Transportation was done on horseback and on foot.
The first post office in Markstay was located in the basement of the home of the postmaster. The current Markstay Post Office at the corner of Main Street and Pioneer Street was constructed in 1976.