Oops!!! Hit Send button too soon ? You can stop your email from being sent in Gmail for a few seconds after hitting the Send Button.Sometimes, It happens that after composing the email,we quickly hit the Send button, but suddenly realize that we forget to mention something in the body or forget to attach certain files.In this case you can perform undo action on the sent mail but only for a few seconds after hitting the Send Button.This is lesser known feature of Gmail, but can be very useful in certain situations.
Here is how to enable Undo Button to cancel a sent Email in Gmail.
  • Undo Sent Feature is part of Gmail Labs,that means, this feature is under testing phase.Click on the Settings Icon in top right corner and ClickSettings.
undo Sent mail in gmail
  • Under the Settings, Look for Labs and Click it.Scroll down until you seeUndo Send and Click the enable button in order to enable the feature.
 cancel sent mail in gmailundo sent mail in gmail
  •  At the bottom, Click Save Changes button to apply the changes.gmail labs
  • By Default ,Gmail gives you time of 10 seconds to undo the sent mail, but you can change it to 5 ,20 or maximum of 30 seconds.For this , You again need to go to  Settings.Under the General tab, look for Undo Send and set theSend Cancellation Period according to you.Click Save Changes button to apply the changes.
setting send cancellation period in gmail labs
  • Next time you send a Email, Undo Button will appear for 30 seconds (in my case) using which you can prevent the delivery of mail to the recipient. 
How to Cancel/Undo a Sent Mail in Gmail