mailin100.dcpserver.de has no CNAME records.
Question and response
Question
dig mailin100.dcpserver.de. NS
Answer
The response has no answer records.
Authority
dcpserver.de. 1125 SOA auth1.artfiles.de. hostmaster.artfiles.de. 2026021701 28800 14400 860400 1800
Additional
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0