nsb4.srv53.net has no CNAME records.
Question and response
Question
dig nsb4.srv53.net. NS
Answer
The response has no answer records.
Authority
srv53.net. 1301 SOA ns1.srv53.net. support.dnshosting.org. 1590167505 1800 600 2419200 1800
Additional
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0