mail.csg.premiumit.com has no CNAME records.
Question and response
Question
dig mail.csg.premiumit.com. NS
Answer
The response has no answer records.
Authority
premiumit.com. 1401 SOA ns1.dnsbycomodo.net. admin.dns.com. 2026022701 10800 864000 7200 7200
Additional
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0