I don’t do it often but I get a fair share of emails with the attachments missing and another email quickly following it with the attachment intact. Google Gmail has just added an “Undo” feature that allows you to retract a sent email for up to five seconds in case you forget an attachment or a CC, etc. When you see the email sending, there will a cancel button you can hit to halt the email in its tracks. This then brings the email back to draft status allowing you to make the necessary changes. What it won’t do is exhume emails that have made it past the 5 second mark. You can enable this option under the Gmail settings tab and then the labs tab in which undo will be towards the bottoms of the list. Easy enough.