Gmail has unveiled an Undo Send button that lets people stop an email message they have just sent.

To turn on the feature, go to your ‘Gmail Labs > Settings > Undo Send’ section. An undo button will then appear on your GMail dashboard afterwards. It will holds your message for five seconds and anything beyond that time, well the email would have been sent.

A great tool if you accidently sent your porn to your boss or mother-in-law perhaps?