The word "autoresponder" originates from the two words "automatic" and "response". An autoresponder is essentially an automated reply to an incoming email.

You've likely experienced an autoresponder when you try emailing a large company's support email address and immediately receive an email informing you that your message has been received.

You've also probably experienced autoresponders when emailing a colleague or business acquaintance who's out of the office on holiday — the "Out of office" reply is a form of autoresponder too.

When sending out a marketing campaign, the larger your audience the more likely you are to receive an influx of responses in the form of autoresponders — both from corporate catch-all mailboxes, and from contacts who are out of the office.

You may also want to set up an autoresponder of your own if you are sending email campaigns frequently and want to ensure your recipients know how their replies are being handled.