title: PayPal responds Fatal Failure for some valid payments
body: <p>When I send the ipn verification request to PayPal it usually works fine, but for some valid payments I am getting 'Fatal Failure' as result instead of 'VERIFIED'.
  What can cause this?</p>
  
  <p>This is the code I am using</p>
  
  <pre><code>$req = 'cmd=_notify-validate&amp;' . file_get_contents('php://input');
  $ch = curl_init($uri);
  curl_setopt($ch, CURLOPT_HTTP_VERSION, CURL_HTTP_VERSION_1_1);
  curl_setopt($ch, CURLOPT_POST, 1);
  curl_setopt($ch, CURLOPT_RETURNTRANSFER, 1);
  curl_setopt($ch, CURLOPT_POSTFIELDS, $req);
  curl_setopt($ch, CURLOPT_SSLVERSION, 6);
  curl_setopt($ch, CURLOPT_SSL_VERIFYPEER, 1);
  curl_setopt($ch, CURLOPT_SSL_VERIFYHOST, 2);
  curl_setopt($ch, CURLOPT_FORBID_REUSE, 1);
  curl_setopt($ch, CURLOPT_CONNECTTIMEOUT, 30);
  curl_setopt($ch, CURLOPT_HTTPHEADER, array('Connection: Close'));
  $res = curl_exec($ch);
  </code></pre>