ns1.mainns.de has no CNAME records.
Question and response
Question
dig ns1.mainns.de. NS
Answer
The response has no answer records.
Authority
mainns.de. 10800 SOA ns1.mainns.de. info.domains.resellerinterface.de. 1772496027 14400 3600 604800 86400
Additional
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0