biscmail.cv.net has no CNAME records.
Question and response
Question
dig biscmail.cv.net. NS
Answer
The response has no answer records.
Authority
cv.net. 2600 SOA authns1.cv.net. abuse.optimum.net. 2013419770 7200 600 604800 3600
Additional
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0