bulk01.brennercom.net has no CNAME records.
Question and response
Question
dig bulk01.brennercom.net. NS
Answer
The response has no answer records.
Authority
brennercom.net. 467 SOA marek.ns.cloudflare.com. dns.cloudflare.com. 2397242853 10000 2400 604800 1800
Additional
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0