public static function isBlacklisted($email) {
        $parts = explode("@", $email);
        $domain = end($parts);

        foreach (self::allDomainSuffixes($domain) as $domainSuffix) {
            if (in_array($domainSuffix, self::$blacklist)) {
                return true;
            }
        }

        return false;
    }