At this point, I have absolutely zero faith in SE's capabilities to implement a working, functional mailbox.

"You asked for it! In the next version update we will be implementing mailboxes for players. We will use the in game mailbox to inform players on the latest SE news. You won't be able to transfer gil or items using the mailboxes, but we have 14 different types of stationary to choose from when you create your letters to other players. At this time, letters are limited to 80 characters, and you will only be able to send letters to people on your friend list... who are online. We hope you're as excited about this addition as we are!"