mail.bdp.blue has no CNAME records.
Question and response
Question
dig mail.bdp.blue. NS
Answer
The response has no answer records.
Authority
blue. 3600 SOA a0.nic.blue. hostmaster.donuts.email. 1772640657 7200 900 1209600 3600
Additional
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0