mta02-bmail.btactic.com has no CNAME records.
Question and response
Question
dig mta02-bmail.btactic.com. NS
Answer
The response has no answer records.
Authority
btactic.com. 10780 SOA dns16.ovh.net. tech.ovh.net. 2025032500 86400 3600 3600000 86400
Additional
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0