Many times it happened that we send an email to wrong person and once mail is sent, we realized that it went to wrong guy. Now what ? Well, Gmail lab introduced a new feature to help you in such scenario. Now you can stop messages from being sent for a few seconds after hitting the send button.
Turn on Undo Send in Gmail Labs under Settings, and you’ll see a new “Undo” link on every sent mail confirmation. Click “Undo,” and it will grab the message before it’s sent and take you right back to compose.
This feature can't pull back an email that's already gone; it just holds your message for five seconds so you have a chance to hit the panic button. If you close Gmail or your browser crashes in those few seconds, it will still send your message.