Gmail adds "Undo Send" feature in Google Labs

Gmail has added an "Undo Send" feature -- you can recall messages you send if you do it within five seconds after clicking on the Send button. To enable the feature, click on the greet lab bottle in the upper right corner of the Gmail page. Find "Undo Send" and click on the "Enable" radio button. Click "Save Changes" at the top or bottom of the page. Once enabled, all e-mail sent will show an "Undo" link at the top during the five seconds before the mail is sent for good.