form action="https://app.getresponse.com/add_subscriber.html" accept-charset="utf-8" method="post">
    <!-- Email field (required) -->
    email: <input type="text" name="email"/><br/>
    <!-- List token -->
    <!-- Get the token at: https://app.getresponse.com/campaign_list.html -->
    <input type="hidden" name="campaign_token" value="aYCbt" />
    <!-- Thank you page (optional) -->
    <input type="hidden" name="thankyou_url" value=""/>
    <!-- Add subscriber to the follow-up sequence with a specified day (optional) -->
    <input type="hidden" name="start_day" value="0" />