mail.dmopp.de has no CNAME records.
Question and response
Question
dig mail.dmopp.de. NS
Answer
The response has no answer records.
Authority
dmopp.de. 264 SOA ns1110.ui-dns.biz. hostmaster.1und1.com. 2017060279 28800 7200 604800 600
Additional
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0