windows support has been enhanced to function checkdnsrr() in PHP 5.3.8

 windows support has been enhanced to functions - checkdnsrr(),
   
checkdnsrr()


     Check DNS records corresponding to a given Internet host name or IP address.
     syntax:bool checkdnsrr ( string $host [, string $type = "MX" ] )
        -Searches DNS for records of type type corresponding to host.


This is a little code example that will validate an email address in two ways:
- first the general syntax of the string is checked with a regular expression
- then the domain substring (after the '@') is checked using the 'checkdnsrr' function

<?php
function validate_email($email){

   $exp = "^[a-z\'0-9]+([._-][a-z\'0-9]+)*@([a-z0-9]+([._-][a-z0-9]+))+$";

   if(eregi($exp,$email)){

      if(checkdnsrr(array_pop(explode("@",$email)),"MX")){
        return true;
      }else{
        return false;
      }

   }else{

      return false;

   }   
}
?>