mx2-pp.mail.rice.edu has no NS records.
NS records for this zone are defined at mail.rice.edu.
NS records for this zone are defined at mail.rice.edu.
Question and response
Question
dig mx2-pp.mail.rice.edu. NS
Answer
The response has no answer records.
Authority
mail.rice.edu. 300 SOA ns2.rice.edu. hostmaster.rice.edu. 2016013130 14400 3600 1200000 3600
Additional
. 0 OPT ; payload 1220, xrcode 0, version 0, flags 0