Look at DNS zone of your domain plugindb.de:
# dig axfr plugindb.de @dns.dns1.de
; <<>> DiG 9.9.4-RedHat-9.9.4-38.el7_3.1 <<>> axfr plugindb.de @dns.dns1.de
;; global options: +cmd
plugindb.de. 86400 IN SOA dns.dns1.de. hostmaster.plugindb.de. 2017020401 28800 7200 604800 86400
*.plugindb.de. 300 IN A 84.200.222.54
core.plugindb.de. 300 IN A 84.200.222.54
imap.plugindb.de. 300 IN A 84.200.222.54
mail.plugindb.de. 300 IN A 84.200.222.54
plugindb.de. 300 IN A 84.200.222.54
plugindb.de. 300 IN MX 10 mail.plugindb.de.
plugindb.de. 300 IN NS dns.dns1.de.
plugindb.de. 300 IN NS dns.dns2.de.
plugindb.de. 300 IN NS dns.dns3.de.
plugindb.de. 300 IN NS dns.dns4.de.
server1.plugindb.de. 300 IN A 84.200.222.47
server2.plugindb.de. 300 IN A 84.200.113.78
server3.plugindb.de. 300 IN A 84.200.222.12
smtp.plugindb.de. 300 IN A 84.200.222.54
plugindb.de. 86400 IN SOA dns.dns1.de. hostmaster.plugindb.de. 2017020401 28800 7200 604800 86400
As you can see you have wildcard subdomain *.plugindb.de Therefore, any subdomain will be resolvable to 84.200.222.54 IP address. Even admin.plugindb.de:
# host admin.plugindb.de
admin.plugindb.de has address 84.200.222.54
# host hahaha.plugindb.de
hahaha.plugindb.de has address 84.200.222.54
# host tututututututu.plugindb.de
tututututututu.plugindb.de has address 84.200.222.54