Undo Sending Your E-Mail

If you make sending a message (E-mail), you can undo the action by enabling the "Undo send" . This will give you the option to take back a message (E-mail) you just sent.

Follow the following steps :

Click the gear icon at the top of your Google-mail page and select Mail settings.
Click the Labs tab.
Find the "Undo Send" lab and select the Enable radio button.
Click Save Changes at the down of the page.
Click on gear icon again and select general tab .
Now you see "Undo send " option here and select the time for undoing a message.

 This thing is applicable  for Google-mail.