You will use autoresponders when you are out of office. (an out of office reply message letting people know that you are not available at present but will get back to them when you are back. The autoresponder will automatically send a predefined message that you have set up to anyone sending you a message.

It is also handy when you have potential clients sending you a message, thanking them for their message and letting them know that you are busy with their request and will get back to them as soon as possible.

Many websites with memberships has this sending an automated message to new members welcoming them.

Autoresponders can also be used to send a link to subscribers or banking details when a client places an order.