An (email) autoresponder is a software program running on a computer
server connected full time to the
Internet . An autoresponder has an
email address . If someone sends an email to an autoresponders email address, the autoresponder automatically and immediately emails this person a standard answer (for example: "Thank you for sending me a message. I will reply shortly"), and at the same time it sends also the incoming message to the person who owns the autoresponder (so the owner of that autoresponder can reply to this email message later on). So, if you send someone an email and you get an answer immediately, you know that you have sent a message to an autoresponder.