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