Undo sent mails

Suppose you clicked on send button too fast or sent the mail to someone else, you can undo this with Gmail. Gmail labs has a feature to undo sent mails. It gives you a grace period of few seconds to undo a sent mail. Turn it on from the Labs tab under Settings.

Once you activate this Gmail labs feature and send a mail. A bubble appears above your inbox for a few seconds with an undo link. Click on the undo link to undo the sent mail.