Sending an email to the wrong person can be disastrous, and Gmail is finally offering some users an "undo" button for emergencies like that. The feature rolled out to users with Android devices worldwide in Google's latest update of its email services. After a Gmail sends a message an 'undo' button will appear on their screen, and they will have ten seconds to click it before the option disappears and the email is sent as usual. The feature was already available on desktop and iOS versions of Gmail, and desktop users even have the ability to choose a time limit they have to 'unsend' a message.