mail.billythorpe.com has no CNAME records.
Question and response
Question
dig mail.billythorpe.com. NS
Answer
The response has no answer records.
Authority
billythorpe.com. 5656 SOA ns1.bondagekitty.com. postmaster.bondagekitty.com. 2025061908 28800 7200 1209600 10800
Additional
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0