smtp.simac.com has no CNAME records.
Question and response
Question
dig smtp.simac.com. NS
Answer
The response has no answer records.
Authority
simac.com. 3582 SOA ns1.premium-dns.net. hostmaster.simac.com. 2026030501 86400 3600 604800 3600
Additional
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0