Few email errors are more embarrassing than sending a message to the wrong person. It happens, and when it does, we all wish we were able to stop the message in its tracks.
With Gmail, you can do just this by enabling the Undo Send option. The name is perhaps a bit misleading, because the main thing it does is delay your message sending, giving you time to catch mistakes.
To enable Undo Send, click the gear icon in the top-right of Gmail. Select Settings and scroll down to the Undo Send option.
Tick the checkbox to enable it, and then choose your preferred delay time from 5, 10, 20 or 30 seconds.
Scroll down and click Save Changes.
Now, any email sent will be delayed, giving you time to undo sending it.
The Your message has been sent notification will contain an Undo action. Click Undo on the notification (within the delay) and your message will reopen for you to correct.