Ever sent and email, only to realize that you made a mistake. Wish you could take it back and prevent yourself from being embarrassed. Well, Google has come up with an experimental feature that lets you undo an email within few seconds after hitting the send button. Lets see how to configure it.
1. Go to the setting icon on the top right of your account. Clicking on it a drop down appears, click the setting tab. 2. It looks something like this, from here jump to the Labs tab. 3.Scroll down to the Undo send application and select Enable. And you are done! Here is the original story.http://gmailblog.blogspot.in/2009/03/new-in-labs-undo-send.html