mx1.proofpoint.com.gslb.pphosted.com has no NS records.
NS records for this zone are defined at proofpoint.com.gslb.pphosted.com.
NS records for this zone are defined at proofpoint.com.gslb.pphosted.com.
Question and response
Question
dig mx1.proofpoint.com.gslb.pphosted.com. NS
Answer
The response has no answer records.
Authority
proofpoint.com.gslb.pphosted.com. 60 SOA ns-sc4.proofpoint.com. ops.proofpoint.com. 166 10800 3600 604800 60
Additional
. 0 OPT ; payload 4096, xrcode 0, version 0, flags 0