iredmail.priv.mcs.de has no CNAME records.
Question and response
Question
dig iredmail.priv.mcs.de. NS
Answer
The response has no answer records.
Authority
priv.mcs.de. 321 SOA ns1.mcs.de. hostmaster.mcs.de. 2026022700 14400 3600 604800 600
Additional
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0