An auto-responder is a predefined email message, which can be sent automatically as a reply to every email received inside a mailbox with this option activated. Two of the most typical examples for employing this function are automated e-mails that one is temporarily out of the office or that an order is received successfully. An auto-responder could also be used as a standard confirmation that the email is received successfully, which may be something quite important in business e-mail correspondence. The message which is delivered can be more or less anything and could be changed based on the conditions and what the auto-responder will be used for. As the feature is activated server-side, there isn’t anything you are required to do manually and you don't need an e-mail app to be active all the time for the automatic reply to be sent to the person sending you an email.