mail01.trustcsi.com has no CNAME records.
Question and response
Question
dig mail01.trustcsi.com. NS
Answer
The response has no answer records.
Authority
trustcsi.com. 170 SOA gns1.trustcsi.com. hostmaster.cpcnet-hk.com. 2024070501 10800 3600 604800 600
Additional
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0