Fatal error: Link-ID == false, Verbindung fehlgeschlagen

Error Message: Link-ID == false, Verbindung fehlgeschlagen
Error Code: 2005
SQL Type: Database
SQL Error: Unknown MySQL server host 'mysql5.exoom.net' (1)
SQL Error Number: 2005
SQL Version:
File: /kunden/exoom.net/lautenschlaeger/energieberater-in/lib/database/Database.class.php (76)
PHP Version: 5.2.17
GUI Version: 2.6.5
DB Build: 1063
Date: Tue, 28 Mar 2017 10:03:45 +0000
Request: /show_cat.php?catID=15&page=1
Referer:

Stacktrace:

#0 /kunden/exoom.net/lautenschlaeger/energieberater-in/lib/database/Database.class.php(60): Database->connect()
#1 /kunden/exoom.net/lautenschlaeger/energieberater-in/lib/database/Database.class.php(517): Database->__construct(...)
#2 /kunden/exoom.net/lautenschlaeger/energieberater-in/acp/inc/init.php(107): require_once('/kunden/exoom.n...')
#3 /kunden/exoom.net/lautenschlaeger/energieberater-in/global.php(35): require_once('/kunden/exoom.n...')
#4 /kunden/exoom.net/lautenschlaeger/energieberater-in/show_cat.php(11): require('/kunden/exoom.n...')
#5 {main}