mail.atmc-dns.com has no CNAME records.
Question and response
Question
dig mail.atmc-dns.com. NS
Answer
The response has no answer records.
Authority
atmc-dns.com. 3600 SOA ns10.atmc-dns.com. hostmaster.atmc.net. 2020080601 10800 1800 1814400 3600
Additional
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0