mx1.paypalcorp.com has no NS records.
NS records for this zone are defined at paypalcorp.com.
NS records for this zone are defined at paypalcorp.com.
Question and response
Question
dig mx1.paypalcorp.com. NS
Answer
The response has no answer records.
Authority
paypalcorp.com. 300 SOA ppdns.paypal.com. hostmaster.paypal.com. 1969046569 7200 600 1209600 300
Additional
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0