RegRu::checkDomain

static function checkDomain(string $user, string $password, string $domain, ?string &$error): ?bool
{
	$domain = mb_strtolower($domain);
	$domain = Encoding::convertEncoding($domain, SITE_CHARSET, 'UTF-8');

	$result = CMailRegru::checkDomain($user, $password, $domain, $error);

	if ($result !== false)
	{
		if (
			isset($result['domains'][0]['dname']) &&
		    $result['domains'][0]['dname'] == $domain
		)
		{
			$result = $result['domains'][0];
			if ($result['result'] == 'Available')
			{
				return false;
			}
			else if ($result['error_code'] == 'DOMAIN_ALREADY_EXISTS')
			{
				return true;
			}
			$error = $result['error_code'];
		}
		else
		{
			$error = 'unknown';
		}
	}

	return null;
}