gdc-smx.connect.guidecom.de has no CNAME records.
Question and response
Question
dig gdc-smx.connect.guidecom.de. NS
Answer
The response has no answer records.
Authority
guidecom.de. 490 SOA ns.ui-global-dns.de. hostmaster.1und1.com. 2017060560 28800 7200 604800 600
Additional
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0