Good news everyone! We now have a functional post office! Here's how it works: on the first floor is a directory. Go in and claim a mailbox. (1-18). Add your name to the sign on the directory (downstairs) and the box itself (upstairs.)
If you want to leave someone an item or a message, use their mailbox upstairs. If you so choose, flip the corresponding redstone torch downstairs so they know they have new mail!
Sadly, being a technology pundit is truly never having to say you’re sorry. You can be wrong for years and never lose your job.—The Macalope