mailin11.prod.datevnet.com has no CNAME records.
Question and response
Question
dig mailin11.prod.datevnet.com. NS
Answer
The response has no answer records.
Authority
prod.datevnet.com. 600 SOA ns01.datev.de. dnsmaster.datev.de. 2603031045 21600 3600 604800 600
Additional
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0