You are going to send an email but by mistake you have sent wrong email or sent email to a wrong recipient. You need to get Gmail Undo Send feature. Gmail Undo send is a feature of Gmail from which you can get your mail back before it receives by recipient.
Undo send gives up to 30 Seconds to change your mind and take back our email before the recipient see it. This will also work when you are going to reply only one sender but by mistake you have select reply to all. Or you are going to send an attachment but forgot to attach the attachment.
How to Enable Gmail Undo Send
First, open your Gmail account. This is only works on Gmail.
Second, click on the gear icon in the upper right corner.
Click on Settings from the drop down menu. Then click on Labs in the top menu.
Scroll down to option “Undo Send” and click Enable.
Then scroll back up to the top and click Save Changes.
That’s it. You have done.
Checking Undo Send
Yes, you could check whether this feature works by sending a test mail. I suggest write an email to yourself and hit Send. When you send email you see undo link at the top of the screen for few seconds.
If you click undo before it disappear then the mail would not be sent. You will see notification that saying Sending has been undone.
Customizing Undo Send (Time Setting)
You can customize the time for this feature. You can adjust the time from 5 to 30 seconds. By adjusting time your email sent to recipients after the time you have set for undo.
To set the time for Undo link appears after you hit the Send button,
Click on the Gear icon,
Then select Settings, click on General, on the left side of the top menu.
Scroll down to Undo Send and choose the Undo Send Cancellation period.
Scroll to the bottom of the page and click on Save Changes. You can change this later if you need more or less time.