function IsEmailAddrValid($email, $check_dns = false)
{ 
  if( 
      (preg_match('/(@.*@)|(\.\.)|(@\.)|(\.@)|(^\.)/', $email)) 
      || 
      (preg_match('/^.+\@(\[?)[a-zA-Z0-9\-\.]+\.([a-zA-Z]{2,3}|[0-9]{1,3})(\]?)$/', $email)) 
    ) 
  { 
    if($check_dns) 
    { 
      $host = explode('@', $email);
      // Check for MX record 
      if( checkdnsrr($host[1], 'MX') ) return true; 
      // Check for A record 
      if( checkdnsrr($host[1], 'A') ) return true; 
      // Check for CNAME record 
      if( checkdnsrr($host[1], 'CNAME') ) return true; 
    } 
    else 
    { 
      return true; 
    } 
  }  return false; 
}