mail2.corenap.com has no CNAME records.
Question and response
Question
dig mail2.corenap.com. NS
Answer
The response has no answer records.
Authority
corenap.com. 2875 SOA ns1.dfw.databank.com. ipadmin.databank.com. 2024022830 7200 3600 1209600 3600
Additional
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0