I don't think there is a way to do this automatically, but I've been using the s...

		cstejerean on March 20, 2009 \| parent \| context \| favorite \| on: Undo Send in Gmail I don't think there is a way to do this automatically, but I've been using the super stars in GMail for this. I use one of them to mark emails that I'm waiting for a reply on, so I can follow up with people if I don't hear from them for a while.