Low-tech Magazine has published an article by Kris De Decker about an almost forgotten predecessor to email: the optical telegraph.
In 1791, Frenchman Claude Chappe developed the optical telegraph. Thanks to this technology, messages could be transferred very quickly over long distances, without the need for postmen, horses, wires or electricity. Within a few years it was possible to send messages throughout Europe at the speed of an airplane — wireless and without need for electricity.
The optical telegraph network consisted of a chain of towers... placed 5 to 20 kilometers apart from each other. Every tower had a telegrapher, looking through a telescope at the previous tower in the chain. If the semaphore on that tower was put into a certain position, the telegrapher copied that symbol on his own tower. A message could be transmitted from Amsterdam to Venice in one hour's time. A few years before, a messenger on a horse would have needed at least a month's time to do the same.
The optical telegraph network was solely used for military and national communications, individuals did not have access to it – although it was used for transmitting winning lottery numbers and stock market data.
A similar network was attempted in North America but never had much success. Kris De Decker's article only describes the more successful networks in Europe.
You can read more at http://www.lowtechmagazine.com/2007/12/email-in-the-18.html.