Gmail's new Undo Send button in case you regret your last email

One of the most popular experimental features to come from Gmail Labs is ‘Undo Send’. Undo Send became one of the most popular features to come from the Labs. The Undo button would exist for a few seconds from the time you hit Send, which was enough time for most users to prevent the message ever leaving their mailbox. It should be noted that the Undo Send feature was seen recently seen in Inbox by Gmail.