An auto-responder is a predefined e-mail, which is sent automatically as an answer to every single email received in a mailbox with this option activated. Two of the most common instances for employing this function are automatic emails that one is briefly out of the office or that an order has been received successfully. An auto-responder can also be used as a standard confirmation that the e-mail is delivered successfully, which may be something quite important in enterprise e-mail correspondence. The message that is sent can be pretty much anything and could be modified depending on the circumstances and what the auto-responder will be used for. As the function is activated server-side, there isn’t anything you have to do manually and you don't need an e-mail program to be enabled all the time for an automatic reply to be delivered to the individual sending you an email.