After sending an email, often the sender wishes if they could have edited the recipient lists or subject or the body or would have canceled the email entirely. Now with some basic settings it is possible to undo the sending process. We can see the details in this post.
How to Achieve it:
In Google email, there is an option to delay the process of sending emails. Leveraging this option, it is possible to un-send an email for a short time just after it has been sent, because technically the email is not yet sent immediately.
In order to enable this option, click the “gear box” in gmail and choose “See all Settings”. Here you will find an option “Undo Send:” set this value to 30 sec. This will ensure that when you send an email, it will be delayed for 30 sec. During this time a popup button will appear towards the bottom left of your email screen. This popup button will allow you to unsend the email.
Using this new feature, it is now possible to unsend and modify the email contents just after it was sent out.