Google announced on Monday that it is adding its new Gmail feature "Undo Send" to the main settings on the Gmail's Web version, which has been around for a while but hidden in Google's labs.Google has announced its new tool in an official blog post: "Previously a popular feature in Gmail Labs, and recently added to Inbox by Gmail, today we're adding 'Undo Send' as a formal setting in Gmail on the web."Undo Send" allows people using Gmail to cancel a sent mail if they have second thoughts immediately after sending. The feature is turned off by default for those not currently using the Labs version, and can be enabled from the General tab in Gmail settings."The new feature enables Gmail users to set a cancellation period of from five to 30 seconds to retrieve an email sent prematurely. Thus, once the user hits the "send" button by accident, a pop-up message will appear at the top of the inbox saying: "Your message has been sent. Undo", which gives a specific amount of time for the user to change his mind.Gmail "Undo Send" can be enabled in the "general" tab of Gmail settings. Under the "Enable Undo Send" option, the user can customize the cancellation period for the feature.