SQL-DATABASE ERROR

Database error in WoltLab Burning Board (2.1.5): Link-ID == false, connect failed
mysql error: Unknown MySQL server host 'db08.kundenserver.de' (0)
mysql error number: 2005
mysql version: unknown
php version: 4.4.9
Date: 19.04.2018 @ 15:31
Script: /mailform.php?subject=Kontaktformular%20von%20Homepage
Referer: