E-mail Check

<?
function checkmail($address) {
  $fp = fsockopen("localhost", 25, $errno, $errstr, 30);
  if (!$fp) {
     echo "$errstr ($errno)<br />\n";
  } else {
     $rset = 0;
     $sender = "<>";
     while (!feof($fp)) {
       $regel = fgets($fp, 128);
       if(substr($regel, 0, 3) == "250") {
         if($action == "mail from") {
           $out = "MAIL FROM:$sender\r\n";
           $action = "rcpt to";
         } else if($action == "rcpt to") {
           $out = "RCPT TO:$address\r\n";
           $action = "quit";
         } else {
           if($rset == 0) {
             $status = TRUE;
           } else {
             $status = FALSE;
           }
           $out = "QUIT\r\n";
         }
       } else {
         if(substr($regel, 0, 3) == "220") {
           if($_POST[host] != "localhost") { $out = "HELO localhost\r\n"; }
           else { $out = "HELO localhost\r\n"; }
           $action = "mail from";
         } else if(substr($regel, 0, 3) == "221") {
         } else if(substr($regel, 0, 3) == "") {
         } else {
           if($rset == 0) {
             $rset = 1;
             $sender = "[email protected]";
             $out = "RSET\r\n";
             $action = "mail from";
           } else {
             $status = FALSE;
             $out = "QUIT\r\n";
           }
         }
       }
       if(!empty($out)) {
         fwrite($fp, $out);
         $out = "";
       }
     }
     fclose($fp);
  }
  return $status;
}

    echo "<h4>e-mail Checker</h4>\n";
    if(isset($_POST[submit])) {
      echo "<table>\n";
      echo "<form action=\"emailcheck.php\" method=\"POST\">\n";
      echo "  <tr>\n";
      echo "    <td colspan=\"2\">Controleren of een e-mail adress echt bestaat.</td>\n";
      echo "  </tr>\n";
      echo "  <tr>\n";
      echo "    <td>E-mail</td>\n";
      echo "    <td><input type=\"text\" name=\"email\" value=\"E-mailadres\" size=\"25\"><input type=\"submit\" name=\"submit\" value=\"Controleren\"></td>\n";
      echo "  </tr>\n";
      echo "</form>\n";
      echo "</table><br>\n";
      if (checkmail($email) == 1 ) {
        echo "<font color=\"green\">{$email}</font> bestaat.";
      } else {
        echo "<font color=\"red\">{$email}</font> bestaat niet.";
      }
    } else {
      echo "<table>\n";
      echo "<form action=\"emailcheck.php\" method=\"POST\">\n";
      echo "  <tr>\n";
      echo "    <td colspan=\"2\">Controleren of een e-mail adress echt bestaat.</td>\n";
      echo "  </tr>\n";
      echo "  <tr>\n";
      echo "    <td>E-mail</td>\n";
      echo "    <td><input type=\"text\" name=\"email\" size=\"25\"><input type=\"submit\" name=\"submit\" value=\"Controleren\"></td>\n";
      echo "  </tr>\n";
      echo "</form>\n";
      echo "</table>\n";
    }
?>