The new Gmail app for iPhone will let you 'unsend' emails
But the biggest new feature is the ability to "unsend" emails shortly after you send them.
To be clear, the unsend feature doesn't mean you can pull an email out of a recipient's inbox after it has been delivered. Instead, Gmail gives you a few extra seconds after you hit send to decide if you want to cancel before the email is actually delivered.
A bar will pop up at the bottom of your screen after you press send. Tapping "undo" will take you back to your email so you can make changes or delete that message you might regret later.
You can download the new Gmail iPhone app here.