Google labs has come out with a really cool feature of Undo Send which lets gives you 5 sec’s timeframe before which can hit the panic button from stopping the mail from being sent to the recipients.

To enable this feature in your Google Mail Account goto Labs under Settings in Gmail.

After that on every sent mail confirmation you will see a new “Undo” link and if you Click “Undo,” before it’s sent you will be taken right back to compose the mail again.