Enabling the Undo Option In Gmail:
- First Login to your G-mail Account
- And then right hit on the wheel button (Settings)
- After hitting on the Button you will be able to see the "Settings"
- After Hitting on the "Settings" by default "General"Tab opens
- Now Switch to the "Lab" Tab
- And scroll down to the end os the page and find the "Undo Send"
- after finding it you need to "Enable" the option and save the options below