public function isEmailBanned($email)
    {
        if (! $this->dbh->query("SHOW TABLES LIKE '{$this->config->table_emails_banned}'")->fetchAll() ) {
            return false;
        };

        $query = "SELECT count(*) FROM {$this->config->table_emails_banned} WHERE domain = :domain";
        $query_prepared = $this->dbh->prepare($query);
        $query_prepared->execute([
            'domain' => (strtolower(explode('@', $email)[1]))
        ]);

        if ($query_prepared->fetchColumn() == 0) {
            return false;
        }

        return true;
    }