If you make a typo or regret sending a message, you can undo the action by enabling "Undo send." This setting gives
you the option to take back a message you just sent.
To enable Undo Send:
1. Click the gear in the top right .
2. Select Settings .
3. Scroll down to "Undo Send" and click Enable .
4. Set the cancellation period (the amount of time you have to decide if you want to unsend an email).
5. Click Save Changes at the bottom of the page.
If you had Undo Send turned on in Gmail Labs, your Undo Send setting will be on by default.