Gmail: Undo Sent Email for a few seconds after hitting the send button

- Login into Gmail (mail.google.com)
- Click on the Gear icon and select Settings
- Select Labs menu
- Search for a lab: "Undo Send"
- Click on "Enable" radio button
- Click on "Save Changes" button
- Try to undo sent email:
--- Compose a message to an email account, recipient example, user@gmail.com
--- Click the Send button (Ctrl+Enter)
--- Click the "Undo" link at the top popped-up message "Your message has been sent. Undo View Message"
--- With this, your email will not be sent