Recently, I visited Europe for the first time, and I was fairly impressed with how modern times allow interglobal telecommunications. Obviously, this was not always the case? How was it in the 19th century? Halfway through the 20th? ect?
Samuel Cunard was awarded the first British Trans-Atlantic mail contract in 1839. He built four steam powered paddle wheel ships and promised at least one mail delivery a week in Boston, Halifax and Liverpool. During the early 20th century, the end points changed to New York City and Southampton and the stop in Halifax was conceded to the Canadian Pacific steamship line.
The Royal Mail kept tight scrutiny on the steamship companies that had Royal Mail contracts. Failure to meet their promised delivery schedules often cost the steamship company their contract. Cunard was able to meet their obligations and developed a close relationship with Britain's Parliament. They were able to get government subsidies to build large and important ocean liners, like the Mauritania and Queen Mary.
Prior to 1839, the Royal Mail did not grant contracts to packet liners on the North Atlantic. In the age of sail, transit times were slower and arrival times far less certain. Prior to 1839, it was hit or miss, but Cunard was soon able to move the mail across the Atlantic in seven days on a very regular basis.