Whoops! You accidentally sent someone an email and now you realize it was a mistake. Maybe you forgot to attach a crucial document, maybe it actually went to the wrong person, or maybe it just wasn't the message you actually wanted to send. Well, the bad news is that by the time you finish reading this tutorial, it will be too late to do anything about it. BUT, the good news is that you can be ready for the next time you need to "Undo Send" in a hurry.
1. Enable Unsend in your Settings. The ability to 'unsend' messages does exist in Google Mail, but it's not enabled by default. To turn it on, click on the gear icon in the upper right hand corner of the screen, then choose 'Settings'. Scroll down the General settings page until you see the "Undo Send" option. You'll need to click the checkbox, and then decide what you want the cancellation period to be. I recommend the maximum time length which is 30 seconds. After you've done this, you're all set to unsend some messages!
2. The day has come! You accidentally sent a message and you want to unsend it. First of all, remember that you need to move fast. You only have a maximum of 30 seconds to unsend your message. Look for a yellow bar at the top of your screen. Usually, this bar just tells you that your message has been sent, but you now have a new option 'Undo'. If you click this link, the message will be 'unsent' and will be returned to your Drafts folder. You can now add that attachment, edit the recipient, or just delete the message altogether and pretend this all never happened. Remember: you only have a limited time to choose this option. After the cancellation period is over (30 seconds in our example), the Undo button disappears and the message is sent.
The Undo Send feature works by actually delaying your outgoing emails emails. If you have 'Undo Send' enabled, it wall delay all of your emails by 30 seconds (or whatever cancellation period you choose). If a 30 second delay isn't acceptable to you, you may want to choose a shorter cancellation period or disable Undo Send altogether.