Auto responder

I have a perfectly working form on my site where users input their email and it goes straight into my email inbox. However, I would like them to recieve an autoresponder message when they input an email. Although the(my) email to which user’s email is sent to has an autoresponder active, my server administrator explained that when an email is recieved, an autoresponder is sent to the form/site and not the user’s email address. He said I would require a code to put in my form to facilitate sending the autoresponder to the user who inputs his email in my site.

Does anyone know a code I could use??