Remember that time you forgot to add an attachment or accidentally hit “Reply All” and looped in everyone else on a confidential thread? Now, Gmail is finally allowing you to reverse the damage you’ve done.
Gmail users can now opt to set time delay between 5 to 30 seconds before sending an email. So, you’ll have that much time to hit “Undo Send” and save yourself.
To enable “Undo Send”, click on the gear wheel icon at the top right of the Gmail display hub and choose “Settings”. The option would be right below.
Google immediately started updating accounts, but it could take two weeks for the feature to roll out to everyone.
What a practical lifesaver!
[Source]