Redstone Mailboxes

Today, I thought to myself, "What is a redstone contraption that is simple, resource friendly, and practical?".  Then it hit me, like it was an envelope sent in the mail!


Redstone Mailboxes!
Making use of the hoppers introduced quite awhile ago, I realized that they could be combined with a minecart to make a, rather simple, two-way mail system.

I'm not saying that i'm the first to make this, as I probably was not, but I do want to say that I did not copy from anyone and that this is original.

NOTE: I'm always on the lookout for great redstoning ideas, whether it be a map or a neat contraption, and you are welcome to send me a PM or comment with any ideas.