public function validateEmails($attribute)
    {
        $items = $this->$attribute;

        if (!is_array($items)) {
            $items = [];
        }

        foreach ($items as $index => $item) {
            $validator = new EmailValidator();
            $error = null;
            $validator->validate($item, $error);
            if (!empty($error)) {
                $key = $attribute . '[' . $index . ']';
                $this->addError($key, $error);
            }
        }
    }