Gmail has finally upgraded their "Undo Send" feature from experimental to a regular part of the email service.
The feature is disabled by default. How do you enable "Undo Send?" Click the gear in the top right and go to Settings. Scroll down until you see "Enable Undo Send" and check the box. You can choose between 5, 10, 20 and 30 seconds as your cancelation windows.
Once you send the email, a dropdown will appear giving you the option to "unsend" if you have a change of heart or you need to make a last-second change.
The "Undo Send" feature has been a part of Gmail Labs since 2009, but it's just now getting the full-feature treatment.
Google made the announcement on Monday, but it could take up to two weeks for the feature to roll out to all accounts.
People currently using the Labs version of "Undo Send" will have the setting turned on by default.