SQL-DATABASE ERROR

Database error in WoltLab Burning Board (): Link-ID == false, connect failed
mysql error: Can't connect to MySQL server on 'rdbms.webmailer.de' (146)
mysql error number: 2003
mysql version: unknown
php version: 5.6.40
Date: 20.05.2019 @ 13:38
Script: /suiyc/index.php
Referer: