public function getWrongEmailUsers()
    {
        if (version_compare($this->appbox->get_version(), '3.9', '>=')) {
            return [];
        }

        $builder = $this->appbox->get_connection()->createQueryBuilder();
        /** @var Statement $stmt */
        $stmt = $builder
            ->select('u.usr_mail', 'u.usr_id', 'u.last_conn', 'u.usr_login')
            ->from($this->table, 'u')
            ->where($builder->expr()->isNotNull('u.usr_mail'))
            ->execute()
        ;
        $rs = $stmt->fetchAll(\PDO::FETCH_ASSOC);
        $stmt->closeCursor();

        $users = [];

        foreach ($rs as $row) {
            if (!isset($users[$row['usr_mail']])) {
                $users[$row['usr_mail']] = [];
            }

            $users[$row['usr_mail']][] = $row;
        }

        $badUsers = [];

        foreach ($users as $email => $usrs) {
            if (count($usrs) > 1) {
                $badUsers[$email] = [];
                foreach ($usrs as $usrInfo) {
                    $badUsers[$email][$usrInfo['usr_id']] = $usrInfo;
                }
            }
        }

        unset($users);

        return $badUsers;
    }