mx.clean.pph4a.pphosted.com has no NS records.
NS records for this zone are defined at pphosted.com.
NS records for this zone are defined at pphosted.com.
Question and response
Question
dig mx.clean.pph4a.pphosted.com. NS
Answer
The response has no answer records.
Authority
pphosted.com. 300 SOA ns1.proofpoint.com. ops.proofpoint.com. 2026240217 1200 120 2419200 600
Additional
. 0 OPT ; payload 4096, xrcode 0, version 0, flags 0