mail.hkr-it.de has no CNAME records.
Question and response
Question
dig mail.hkr-it.de. NS
Answer
The response has no answer records.
Authority
hkr-it.de. 2558 SOA ns.udag.de. hostmaster.united-domains.de. 2024101751 10800 3600 604800 3600
Additional
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0