Undo send Gmail

Stop messages from being sent for a few seconds after hitting the send button.

Step1: Login Gmail

http://www.gmail.com

Step2: Click to Settings LAB

http://mail.google.com/mail/?shva=1#settings/labs

Step3: Enable "Undo Send"
Step4: Final, Click to "Save Changes"

After your email Sent, a new Undo button on the Banner will display. You can click to that if you want to Undo send.

P/S: In this LAB Settings, you can Enable "Forgotten Attachment Detector"