As of the beginning of this year (2016) the S'shamath messenger system has gone live and is working. I tested this as a DM with another player. Messengers can be dispatched and will deliver their message to the target player. They cost 50gp to send. S'shamath only at the moment. These messages can be pending delivery for at least a month, so they have obvious value to communicate in-characterly between players.
Please use these NPCs with the maturity we are accustomed to. It is my understanding that they are an exception to the rule that players may not roleplay what NPC's should do. In this case you can tell the messenger what message to deliver to his target.
Obviously if its a criminal message there are still rule concerns. Hiring a messenger to deliver your evil plans verbally is not something that messenger would presumably consent to. But there are exceptions to this as well: S'shamath contains a number of messenger types:
- Slaves (from the Bazaar slave master)
Servitors (School of Mages)
Gloura's (Bar)
Drow (I don't know where)
Duergar (Spires)
And probably more. Only Rasael knows.
Thanks to all that took part in developing this feature. It's like having a minor sending spell available for everyone 