A breathalyzer for your laptop ... if you're too tipsy to do the math, you probably shouldn't send that email.
One more reason Gmail is the best email to use -- mail goggles.
"Called "Mail Goggles," the Gmail add-on makes sending e-mail from Gmail more difficult during certain times that you can set manually (while sober, that is). How does it do this? If you have Mail Goggles installed—which you can do by going to the "Labs" tab under your Gmail settings and turning them on—it will force you to answer a series of math questions before sending out any new messages." -- From ars technica
The google site