mint.myrasec.de has no CNAME records.
Question and response
Question
dig mint.myrasec.de. NS
Answer
The response has no answer records.
Authority
myrasec.de. 1367 SOA a.myradns.de. support.myrasecurity.com. 2771997765 16384 2048 1048576 2560
Additional
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0