smtp.mtficore.net has no CNAME records.
Question and response
Question
dig smtp.mtficore.net. NS
Answer
The response has no answer records.
Authority
mtficore.net. 637 SOA dns1.ficolo.net. hostmaster.ficolo.net. 2020051901 28800 7200 604800 86400
Additional
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0