Communication in the Known World
by HåvardPostal Services:
Cursus Publicus, a postal service similar to the Pony Express was established by the Romans in 14 AD. Sadly, with the collapse of the Roman Empire this service disappeared, and was not replaced until modern times.
I'd say something similar to the Cursus Publicus exists in Thyatis (although halting), Ylaruam and Darokin (where it may even be known as the Pony Express). The service is however expensive and not always reliable as Riders may encounter all sorts of hazards.
Caravans:
Caravans are more slow moving, but a cheaper version than the Postal Service.
Homing Pigeons:
This is probably a more reliable and quicker service. It was first developed by the Ethengars and Ylari, but is now used all over the Known World.
Overseas Messages
Most communication is probably delivered by ships and riverboats. Most Known World countries have coastlines or large rivers running through them. Minrothad and Ierendi probably rely almost completely on this form of communication
Fire Beacons
Fire Beacons, similar to the ones used in Return of the King are probably used in the Northern Reaches to warn against attacks against the kingdoms. These were also used in RW Scandinavia in Viking times.
Smoke Signals
Much more developed than the Fire Beacons, this form of communication is widely used in Atruaghin and can rely quite detailed messages.
Printing Press:
Gutenberg's Printing Press was invented in 1455. In the Known World I would say this is a relatively new invention and not at all widespread. Almanacs did not exist until AC1010, and then probably also only in limited circulation. Religious texts would probably be what this is most used for, such as the Book of Jowett, which IMC forms the basis of the Church of Karameikos.
Newspapers
According to this page, Newspapers appeared as early as AC 1450 in Europe, though from what I understand these were quite different from what know of as newspapers today. The Romans also had some sort of "newspaper" apparently, so it is natural that something of this kind exists in the Known World. Probably more like a collection of announcements from the rulers of each country sent out various towns and villages, although Heralds would likely be more widespread.
Magic
Magic is expensive, but should be available to most nobles (Baron and above), though it is still expensive and of limited use since you will have a limited number of spellcasters and you might want them to memorise other spells besides communication spells as well. Glantri is obviously the most extreme here where nobles have access to a well developed communications service based in magic. Overall in the Known World, I'd say magic is not as efficient as the Telegraph on its introduction in the real world in 1880.