Gmail adds oops button – Undo Send
The engineers at Gmail are continually tweaking Gmail, adding new features. These features are nice additions, but I wonder if they aren’t muddying the application with too many features.
Undo Send, the latest change, adds the ability to stop a message from being sent after you click on the Send button. The undo capability lasts a few seconds and is not user-editable. I have a similar feature enabled in Microsoft Outlook, where I instruct Outlook to wait 60 seconds before sending any email. The Thunderbird add-on Send Later provides similar functionality.
You will find the Gmail feature in the Labs section of Settings.

Undo Send

Gmail Labs description
Categories: google