mxmta.prod.bellnet.ca has no CNAME records.
Question and response
Question
dig mxmta.prod.bellnet.ca. NS
Answer
The response has no answer records.
Authority
bellnet.ca. 900 SOA tor63vnszp07.srvr.bell.ca. dns-admin.bellglobal.com. 7994 10800 3600 2419200 900
Additional
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0