Google has made email unsend an official feature in Gmail. This feature was available for years, hidden under the “Labs” beta section. It is now open, first to Gmail personal account and for the web version of Gmail. With this feature enabled on your Gmail account, you can unsend email up to 30 seconds after you hit “Send”.
To enable email unsend, goto Gmail.com Settings page under General tab. Scroll down to locate “Undo Send”.
Click on the tick box to “Enable Undo Send”. You also will need to choose how long (either 5, 10, 20 or 30 seconds) is the cancellation period. Click the “Save Changes” button at bottom of the page to save the setting.
The next time you send an email, a thin yellow box with the text “Your message has been sent” will appear on the top of the screen just below the search bar.
Click the “Undo” button to stop the email from sending. Do it quick as the undo option will disappear once the cancellation period is over.