Gmail adds a new labs feature to undo send mail. This feature can retrieve the sent message.
Gmail will hold the message for 5 seconds after hitting send button. This feature is quite useful when you press send button accidently before finishing your message or forget to attach file. You don’t have write a “Oops” message because you can undo now. But remember that the message can be retrieve only with in 5 seconds.
It will also make your email to deliver in more then 5 seconds.
Don’t forget to enable the “Undo Send” feature from Gmail Labs. It is turned off by default.