The back slot was cut so the "mailman" can collect the mail and deliver it. We decided to make the back a little more colorful. So far it has been getting lots of use to hold blocks and the numbers from his floor mat. Over the next couple of days I'm going to add more mail related stuff, such as envelopes, stickers for stamps, and some junk mail (which we always seem to have plenty of).
Have you ever had a mail center? What have you created with a cardboard box? I'm always interested in other ideas!