Something

<?phpfunction 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("@",$email)),"MX")){        return true;      }else{        return false;      }   }else{      return false;   }   }$email = '123@gmail.com';if (validate_email($email)){	echo 'valid';}else{	echo 'Invalid';}?>