How To Enable Undo Send Option In Gmail

If you forget some text or attachments in the mail you sent then you can undo by enabling "Undo send". To enable the option do the following

Step 1 : Login to your Gmail account and click the gear in the top right corner

Step 2 : From the drop down menu select Settings.

Step 3 : Scroll down and see the option Undo Send: and check the box Enable Undo Send

Step 4 : Click Save Changes at the bottom of the page.