mta.us.confirmit.com has no CNAME records.
Question and response
Question
dig mta.us.confirmit.com. NS
Answer
The response has no answer records.
Authority
confirmit.com. 874 SOA udns1.cscdns.net. hostmaster.cscdns.net. 2018082969 10800 1800 1814400 86400
Additional
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0