For most people, written letters are the most common form of long range communication. Carried by either formal or informal mail services, or sometimes by animal messengers, letters are the easiest and simplest method of sending information to people elsewhere. Some regions of the world have formal services to transport mail - in Viridia, for example, the Imperial Post Carriers travel the roads of the Dominion on a set schedule, picking up and delivering letters and packages as they go. In most places, however, these services have more of an informal nature, with travelers volunteering to carry mail intended for the same destination in which they are already headed, in the hopes others will return the favor for them later.
Some organizations take mail carrying a step farther. Songbird Mail Services, based in Tirione, has begun to deploy clockwork birds to deliver notes farther and faster than land-based travel would normally allow. Though they have the backing of some of the larger Tirionite conglomerates, in particular the Silver Falcon Company, Songbird has yet to make a notable impact outside the coastal cities of Tirione.
In the coastal cities of the eastern Chaska Sea, some lighthouses are fitted with movable mirrors that can be used to reflect light in certain patterns. Directed at other lighthouses along the coast, operators at other towers can decode a meaning from the patterns of flashing lights. As this method of communication has a rather limited range, most messages transmitted in this manner are broadcast with a "repeat" instruction, telling the next lighthouse down the chain to send it along. In some parts of the eastern Chaskan coast, lighthouse operators busy themselves with these coded messages all night long when in favorable conditions, with the flashing lights visible from miles away. This carries with it many downsides, as adverse weather conditions can easily render this method of communication unusable.
Elsewhere in the world, drums are used in much the same way as the lighthouse signals, passing coded communications along using sound instead of light. In some parts of the Depths, particularly among dwarven and duergar communities, seismic hammers function similarly, impacting shockwaves into the earth in translatable patterns.
Magical means of long range communication tend to be expensive and carry with them many limitations. Though a spell like Sending works across any distance, and even across planes, the limit to message length and the few times even a skilled mage can cast it per day means that it is simply not an option for the vast majority of people. Some wealthy and powerful individuals rely on networks of mages familiar with each other to coordinate across long distances, but this is highly uncommon. In some places magic items enchanted with Sending are used - the underwater cities of the Chaska, for example, make heavy use of Shells of Sending.
Though it carries even more limitations in some ways, spells like Telepathic Bond can be used to remove the restriction regarding a maximum number of words per message.
To aid in coordinating between their deep sea settlements, the engineers of Barazar El have developed a device they call a tapwire. Thin metal cabling connects all of the underwater cities, with the central hub of the network in Pelagic Frontier. Magical pulses are transmitted along the tapwire, and received quickly at all other settlements despite the great distances between them. The tapwire cables are inspected and maintained regularly. The tapwire is used on an everyday basis for regular communication between the settlements, though use is usually restricted to practical matters.