Stop Inappropriate Gmail Messages From Going Out With Undo Send

Many of us have sent angry or nasty comments in a Gmail email, only to regret it moments after hitting Send – or you remember that you didn’t attach the attachment you referenced in the email (hate with that happens!). If you have ever found yourself in either of these situations, rejoice, because Gmail’s Undo Send feature will help prevent them from happening again.
This handy feature delays the sending of your messages by 5, 10, 20, or 30 seconds, thereby giving you a small window during which you can hit an “undo” button to prevent your message from going out.
To enable Undo Send, go into your Gmail Settings and hit the Labs tab. Scroll down and enable Undo Send, then hit the Save button (and while you are in there, you can peruse some of the other cool features that the people at Google Labs have created). Next, go to the General tab and set your “cancellation period” in the Undo Send section. Hit the Save button and exit Settings.
Better to never say anything snarky in an email message, but nice to have Undo Send if you are having a bad day.