So, your friend couldn't get through the one-way time portal before it closed, and as you're standing there wondering what to do, this guy from the Post Office comes up and says that he's got this letter, posted 80 years ago, and addressed to you. Turns out your friend spent ten years building a machine to stop the Big Bad, and he sealed it away right beneath where you're standing now. As you read it, you can't help but marvel that the message actually made it through the postal service. futureme.org allows you to do this yourself. Examples :