mx.junkemailfilter.net has no CNAME records.
Question and response
Question
dig mx.junkemailfilter.net. NS
Answer
The response has no answer records.
Authority
junkemailfilter.net. 1216 SOA ns.reality-dns.com. dns.reality-dns.com. 2019072900 28800 900 604800 7200
Additional
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0