Tell me if this sounds familiar: You've agonized over an important e-mail, read it over a few times and finally muster up the courage to hit "Send." Then, as you breathe a sigh of relief for finally completing it, you see that you've spelled your recipient's name wrong -- "Katie," not "Katy," or "John" instead of "Jon" -- left a crucial sentence unfinished or maybe written "accept" instead of "except."

Oh. No. Where's the undo button when you need it?

Now Google's baked one right into Gmail thanks to an "Undo Send" feature the company's added to all accounts. The feature has long-been available as an add-on through the Google Labs service and is also available on Google's clean and mobile-focused mail app, Inbox. But now hundreds of millions of people who have Gmail addresses can call back their mistakes, too.

As long as they catch it within 10 seconds, that is.

The feature will show up in the settings menu on Gmail's Web site. The option is off by default, although those who've already had it enabled won't have to change any settings.

If you want to stop your fat-fingered or autocorrect Gmail typos on mobile devices, you'll still have to turn to Inbox for now. And if you want to see more of the wacky features that you may want to sign up for in the future, open the "Labs" tab in your mail settings and flip it on.

Not all the features graduate to the big time, however. Google reserves the right to yank any of its experimental features without warning at any time --  so don't get too attached.