Whoops! Did you type in the wrong email address? Perhaps the address of the very person you were complaining about in the message? Hope it wasn't your boss. If you're using Gmail you can activate an optional feature called "Undo Send" that will give you a thirty second safety window to take back that email after you've hit the "send" button. Now you need to have this feature turned on before you start writing emails, it's not something you can reach for after you've made the mistake. To find it click on "Settings" from your main Gmail window. Then "Labs" from the options that appear, and scroll down to the bottom.

Google's Labs section is where the company places features that are experimental or that they think will only appear to a minority of users. Undo Send was one of the first of these add-ons, but when it was first launched it only offered a 5 second delay, now it can be set for as long as 30 seconds, a great deal more helpful if you're the type who needs a moment to panic or hyperventilate. If you're wondering why this might not be a standard feature, it's because it holds onto every email you send for 30 seconds before actually sending it. For many people, having a delay added to all their emails isn't worth the safety net. Thanks to the Google Operating System blog for spotting it.