function validateUser($user)
    {
        $user_lc = strtolower($user);
        $legalCharacters = "abcdefghijklmnopqrstuvwxyz0123456789!#$%*/?|^{}`~&'+-=_.";
        $s = strlen($user);
        if ($s == 0) return false;
        if ($user[0] == '.' || $user[$s - 1] == '.') return false;
        else if (strpos($user, '..') !== false) return false;
        else for ($i = 0; $i < $s; $i++)
        {
            if (strpos($legalCharacters, $user_lc[$i]) === false) return false;
        }
        return true;
    }

    function check_address($email, &$error)
    {
        $atCount = substr_count($email, "@");
        if ($atCount != 1)
        {
            $error = "Invalid email address.";
            return false;
        }
        $atPos = strpos($email, '@');
        $user = substr($email, 0, $atPos);
        $domain = substr($email, $atPos + 1);
        if (!validateUser($user) || strlen($domain) == 0)
        {
            $error = "Invalid email address.";
            return false;              
        }
        else if (!checkdnsrr($domain,'MX'))
        {
            $error = "Could not find server '" . $domain . "'.  Please check your email address and try again.";
            return false;
        }
        else
        {
            return true;
        }
    }