mailhost.bdmail.net has no CNAME records.
Question and response
Question
dig mailhost.bdmail.net. NS
Answer
The response has no answer records.
Authority
bdmail.net. 600 SOA dns1.bdmail.net. root.dns1.bdmail.net. 2025010501 3600 600 2419200 600
Additional
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0