An auto-responder is also known as an auto-reply, autoresponder, mailbot, autobot and email-on-demand. They are special email accounts, that when someone sends an email to it, it will auto- matically reply to the sender, with a pre-written message. No matter how many people send an email to the auto-responder address, they will all get the same pre-written message auto- matically, usually within a few minutes.

The pre-written message, which the autoresponder owner writes himself, can be a vacation reply, sales letter, confirmation notice, or a response to a web form submission.