mta000.mx.mpssec.net has no CNAME records.
Question and response
Question
dig mta000.mx.mpssec.net. NS
Answer
The response has no answer records.
Authority
mpssec.net. 2828 SOA ns11.mpssec.net. hostmaster.anubisnetworks.com. 2025111042 7200 3600 604800 3600
Additional
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0