From Sanctuary Shard
We have a very useful custom postal service available via the Postmaster NPC. The basic postal system allows you to send a container or book to any other character (you can search by name), send items COD, and order custom items from crafters.
You can also register as a crafter, which will mean you receive requests for orders for that craft. The opposite side of that part of the system, the postmaster sells an item called an order deed book. You can set the receiving craft for it and write in it what you want, and anyone registered with that craft will receive it, and can accept it if they want to fulfill the request.