Adding to its arsenal of features that can save you from yourself, Google is launching a Gmail Labs feature called "Undo Send," that lets you abort the sending of any Gmail message--if you use it within five seconds.
Other user-preservation features already available include Gmail's capability to watch for words like "attached" in the body of an e-mail and to alert you if there are no attachments to the message; and a feature in Google Apps (the corporate version of Gmail) that puts orange borders around the names of e-mail recipients that are not inside your company--to alert you to not send confidential information where you shouldn't.
Also, last year Google launched the "Mail Goggles" Labs feature that prevents you from sending e-mails during the small hours of the morning unless you pass a simple math test. It's designed to prevent drunk e-mailing.
Undo Send is a much smarter feature. We've all regretted pressing "send" on e-mails. Sometimes we realize, too late, that our message is a "reply all" when it shouldn't be. Or that we spelled something wrong. Or that we were angry and shouldn't have sent it at all. Undo Send lets you snatch an e-mail back before it gets sent out. But you have to act fast.
Google product manager Keith Coleman told me that internal testing of the feature, which was created by a Google engineer in Japan as a side project, indicated that five seconds was an appropriate compromise between the ability to recall an errant message and the need to not introduce lag to e-mail conversations. "Adding a delay could be potentially frustrating," Coleman said. I'm not sure the rest of the world is as agile with the mouse as Google's internal testers, but Coleman also told me there's an option to increase the un-send time window to 10 seconds. "We may decide to add longer options," he said.
I'm one person who'd like the option to introduce a longer waiting period, or an "outbox" where queued messages reside for a minute or two before being sent. This is what I do with mye-mail client, Outlook, and Gmail users can get a similar function if they switch to offline mode before they start composing messages. But for most users, who run Gmail in online mode, Undo Send is a good emergency valve.
To activate the Undo Send option, click on "Settings" in Gmail and then the "Labs" tab.
Read more on the Official GMail blog.