How to post to remote url on form submit
You can try something like this

$request_url = 'http://your-url.com';
$request_headers = array('Content-Type' =&gt; 'application/x-www-form-urlencoded');
$request_method = 'POST';
$request_retry = 2;
// form values you want to post
$form_values= array('apple' =&gt; 'red', 'banana' =&gt; 'yellow', 'pear' =&gt; 'green');
$data = http_build_query($fruits, '', '&amp;');

// Send the request.
$response = drupal_http_request($request_url, $request_headers, $request_method, $data, $request_retry);

if ($response-&gt;code == 200) {
  $form_state['redirect'] = array('campaign/thank-you');
}
else {
drupal_set_message(t('There was a problem with your submission. Please try again later.'), 'error');
}


I haven't tried it but let me know if it works.