mail.sassmann.nrw has no CNAME records.
Question and response
Question
dig mail.sassmann.nrw. NS
Answer
The response has no answer records.
Authority
sassmann.nrw. 2778 SOA ns3.inwx.de. hostmaster.inwx.de. 2026021601 10800 3600 604800 3600
Additional
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0