javascript验证邮件地址和MX记录的方法

// Tests for a valid email address and optionally tests for valid MX records, too.
function is_valid_email($email, $test_mx = false)
{
  if(eregi("^([_a-z0-9-]+)(\.[_a-z0-9-]+)*@([a-z0-9-]+)(\.[a-z0-9-]+)*(\.[a-z]{2,4})$", $email))
    if($test_mx)
    {
      list($username, $domain) = split("@", $email);
      return getmxrr($domain, $mxrecords);
    }
    else
      return true;
  else
    return false;
}