Sometimes when sending an email a mistake may be seen and Google now allows 10 seconds to completely re-call the message for further editing

http://thenextweb.com/apps/2015/06/25/after-gmail-googles-inbox-gets-an-undo-send-button/

It took Google six years to add an ‘Undo Send’ feature to Gmail. Thankfully, the company didn’t waste much time adding it to its Inbox app.  You have 10 seconds to hit Undo after you send a message.  The feature has been around for a few weeks; Google is highlighting that it’s now available by default on Inbox’s Web, Android and iOS apps.