Vehn'garane Phasarium communication

The Vehn'garane clan based economy, dispersed clan settlements and credit system means that often the main clan branch needs to be updated on any payments to other clans. Similarly to update about liquid funds being exchanged in a location, and other requests.
For that purpose, one Vehn'garane has invented a system of using two Phasarium crystals, one for sending and one for receiving, and a kind of a Morse code to communicate. A kind of a magical telegraph system. It uses red Phasarium (cheapest and safest and most abundant), amd the way it works is by binding two crystals together, one can cause the other to glow with a small amount of Mana.
That way, using short and long glows, a message in Morse can be sent. The system was invented for its use in the clan economy, but with time its use was spread to passing other important clan messages, and later on more and more nessages. In later ages, it also found more usage between different clans etc.
This technology introduced the role of clan remote communicator.
Originally only two crystals can be bound together, meaning that for messages to be relayed further, they need to pass several communicators.
At first, the investor's clan was the only clan to use it. With time, other clans paid that clan to install and maintain their own networks, given the investor's clan prestige. Eventually though, other clans cracked that technology.
Remote communicators would be sent to settlements in groups in order to take shifts on the communication crystal of the clan's branch there.
Eventually, other (non Vehn'garane) people that lived next to clan branches would start to pay some clans to relay messages across long distances without sending a messenger, saving time, but at a cost not all people could afford.
Of course, using that service would mean revealing that message to all communicators relaying the message, which means that not all messages are suitable to be sent that way.
Also, since one has no way of ensuring who is on the other side, many foreigners don't trust that system, and in fact it was abused by foreigner magic users to intercept messages, increasing the distrust. Some rival clans might also try to steal the crystals to interrupt their rivals.
At the end, as crucial as it is to Vehn'garane economy and governance, due to those factors, some societies mistrusting the elves amd the Vehn'garane's limited geographic distribution (and zealous guarding of the technology), thos technology found only extremely limited use outside Vehn'garane society.