Google has added an experimental feature to Gmail, allowing users to recall email they have sent by mistake. The feature can grab messages before they are delivered and is being rolled out to users worldwide.
Adding to Gmail's features destined to save you from embarrassment, Undo Send lets you abort the delivery of any Gmail message within moments of sending it. Undo Send can be activated from the Settings/Labs tab in Gmail.
Once the feature is activated, a new 'Undo' link will appear next to every sent e-mail confirmation. When clicked, 'Undo' will take you back to the composing window and confirm the retrieval of the email.However, 'Undo Send' doesn't really recall a message that has been already sent. The feature only holds emails in a queue for five seconds, giving you time for second thoughts - though some already argue that this is not long enough.
Other ways not to send a message in Gmail include previous Labs features such as the Forgotten Attachment Detector (pinging the lack of an attachment if it was mentioned in the body) and Mail Googles (which asks you to answer simple maths problems before sending emails).