mx.123.net has no CNAME records.
Question and response
Question
dig mx.123.net. NS
Answer
The response has no answer records.
Authority
123.net. 3572 SOA ns2.distance.net. dns.distance.net. 2026022701 3600 600 1209600 3600
Additional
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0