ns-sc4.proofpoint.COM has no CNAME records.
Question and response
Question
dig ns-sc4.proofpoint.COM. NS
Answer
The response has no answer records.
Authority
proofpoint.com. 1146 SOA ns1.proofpoint.com. ops.proofpoint.com. 2018114807 28800 7200 604800 1200
Additional
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0