To make a form which will capture an email address, add it to a Subscribable Mailing Lists then send an auto-responder, use the below html for the form.
<form method=POST action="http://Your-Domain-Name.com/cgi-bin/formmail.cgi"> <input type=hidden name=recipient value="Autoresponder-name@Your-Domain-Name.com"> Email Address: <input type=text name=email size=15> <input type=Submit value=submit form> <input type=Reset value=reset form> </form>