apollo.centron-mailhost.de has no CNAME records.
Question and response
Question
dig apollo.centron-mailhost.de. NS
Answer
The response has no answer records.
Authority
centron-mailhost.de. 988 SOA ns.internet1.de. hostmaster.internet1.de. 2022092201 3600 900 1209600 1800
Additional
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0