In Bomboria the first post office has opened. There you can buy letters and writing pens, the shop keeper explains you how to write letters. Letters can be put in mailboxes which have been added near some houses. As you can see in the screenshot, people also put some other weird stuff in the boxes
These new letters & mailboxes will also be used for the house building system we will add in a few days. It is possible to close the mailbox with a key so that only you or the post man of your kingdom can open it.