Whether you notice a typo, send to the wrong address, forget to add that attachment, or immediately regret what you wrote once you click Send, you have the option to undo your sent email.
After you click Send on any email, an Undo option will appear in the bottom left of the screen. You'll have a five-second window to recall the email. After that time, it will be sent permanently.
After clicking Undo, you will be taken to the draft of the email you had planned to send, where you can make further changes, save for later, or delete entirely.