mx01.goneo.de has no CNAME records.
Question and response
Question
dig mx01.goneo.de. NS
Answer
The response has no answer records.
Authority
goneo.de. 121 SOA ns1.goneo.de. hostmaster.goneo.de. 2026012301 10800 3600 604800 300
Additional
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0