mx03.eth-services.de has no CNAME records.
Question and response
Question
dig mx03.eth-services.de. NS
Answer
The response has no answer records.
Authority
eth-services.de. 600 SOA uno.eth-services.de. hostmaster.eth-services.de. 2021051008 28800 7200 604800 600
Additional
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0