New Delhi: Do you sometime thought that why did you sent that e-mail in Gmail? If you don't know there's a feature which lets you undo an email sent through Gmail. Most people don't know about this feature since it is hidden. Since the Undo Send feature is part of Gmail Labs, you'll have to navigate to the Gmail Labs page to activate it.By default, Gmail gives you a 10-second window of time in which you may undo a sent e-mail, but you can also change it to 5, 20 or 30 seconds. Go to Settings > General > Undo Send, and select a cancellation period up to 30 seconds.Here's a quick guide to avoiding social and workplace faux pas with the click of a button. 1. On the right hand corner of your Gmail account you'll find the gear icon. Select Settings from the dropdown menu.2. Now choose Labs from the row of tabs.3. Scroll all the way to the bottom where you see Undo Send and click Enable.4. Hit Save Changes at the bottom.Note, features in Gmail Labs are experimental and may change, break, or disappear at any time.(The post originally appeared in Business Insider)