mailin.wtnet.de has no CNAME records.
Question and response
Question
dig mailin.wtnet.de. NS
Answer
The response has no answer records.
Authority
wtnet.de. 338 SOA dns1.wtnet.de. hostmaster.wtnet.de. 2026022301 3600 900 3600000 600
Additional
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0