Set an "Undo Send" Grace Period in Your Gmail Account
If you have ever hit send too early on an email and wished that you could take it back, now you're in luck. As announced on the Google Apps Updates Blog, beginning today Gmail has setting for all users (previously only available to Gmail Labs users) that allows anyone to un-send an email up to 30 seconds after it has been sent. "Undo Send" is a setting that you can enable in your Gmail/ Google Apps mail under the general settings panel. You can find that panel by opening the gear icon in the upper-right corner of your inbox.