This is the tutorial to undo your sent email from gmail. You can't actually bring that mail back from the receiver's inbox once sent but you can stop that message on its way. In your gmail account there is feature about which most of the people are unaware of. Have you heard about gmail labs, that page which contains some really useful tools for your mailbox and are currently going through evaluation and other things. Follow the steps below to undo sent mail in gmail.

1. Log in to your Gmail account and click on the settings option on the top
2. Check for the "Labs" Tab in your settings
3. Scroll down, Near the bottom you will find an Undo send app for Gmail by Yuzo, select "Enable" option beside the app and then save your settings.

Now you are done, By default the undo time is 10 seconds, but if you want, you can customize it by going to your general settings.

Now, whenever you will send an email in the sent mail notification option (appears just after sending in yellow background) you will see an Undo option which you can use only within the selected time.