At the end of my second playthrough of Bastion, I was roaming around one last time around the Bastion area and noticed, to my surprise, a mailbox at the bottom right corner of the central hub. I hadn't seen this before, but apparently it had been there most of the game. I can interact with it, but I just get a witty comment or two from the narrator.
While I can't imagine that the Bastion gets much mail, I feel as though there might have been some sort of purpose for this mailbox other than atmosphere. Am I wrong, and is the only reason for the mailbox to add atmosphere? Or is there some sort of reward or backstory revealed for checking in on the mailbox often or at the right times?