Gmail labs added a new feature “Undo Send” by which you can recall your send emails within 5 seconds after hitting the send button.
Remember to enable the “Undo Send” feature from Gmail > Settings > Labs. It is disable by default.
Once you’ve enabled this feature, you have two options to call back a sent message.
Either way, you have to react quickly(with in 5 seconds).
Go ahead check it out.