Note: I mentioned a fixed price, but just mention in your application, how much it would cost.
There used to be a site called "emailtimemachine.com". It is down now.
What it did was, you could go to the website and just type in a to address and a "from" address and you could also enter the time stamp that you would like the email to have. Then you hit send.
Then, if you login into the "to" email account and check the email, you would have actually received the email from the "from" address that you gave and the date/time would be the date and time that you entered in the application.
Can you replicate this. I think they used bluehost server for their infrastructure. but I am sure that you can use anything comparable.
please mention the code word back to the future in your application or else it would be rejected.