Can I stop or ‘un-send’ an email I sent by mistake?

1. Ya now you can do that, just follow my instruction
   

   

   
   

   
   

   Sometimes we send an e-mail to someone, as soon as press send button. So realize that maybe something went wrong. With all of us, sometimes it is surely. After sending the email and we are thinking that I can cancel it. But now it is really possible to cancel the email, if you want to cancel any e-mail, use below method.But you have only 30 sec to undo the send mail.
2. Here's how it works:
3. 1. Click the gear icon in the top-right corner of your Gmail window and select Settings from the dropdown menu.
   2. In general setting scroll down to the bottom where you see Undo Send and click Enable.
   3. Select a send cancellation period upto 30 seconds.
      
   4. Hit Save Changes at the bottom.

Now when you send an email, the yellow dialogue that displays "Your message has been sent" will also give you the option to Undo. Click it, and the email will reopen, un-sent, in the composition window.

For now, Undo Send feature is not available for the Gmail mobile app for smartphone devices. However, the company is planning to roll out the feature for the mobile app soon.