Well, Google came up with Gmail Paper last year. So how could they top the 2007 Edition. Here's how:
They must have been peeking at the Hallmark e-cards feature request list. Enjoy!
Check out the specs at: http://mail.google.com/mail/help/customtime/index.html and their formula for a maximum of 10 emails per year:
Their findings:
N = Total emails sent
P = Probability that user believes the time stamp
φ = The Golden Ratio
L = Average life expectancy