"'Undo Send' allows people using Gmail to cancel a sent mail if they have second thoughts immediately after sending," Google said in a blogpost.
"Previously a popular feature in Gmail Labs, and recently added to Inbox by Gmail, we're adding 'Undo Send' as a formal setting in Gmail on the web," the company said.
The new tool delays delivery of emails from five to 30 seconds after the send button is pressed to give users a chance to stop an email that was sent, it said.
The feature is turned off by default for most users and can be enabled from the general tab in Gmail settings, it added.