ext-icdrelay1.mx.pearson.com has no NS records.
NS records for this zone are defined at pearson.com.
NS records for this zone are defined at pearson.com.
Question and response
Question
dig ext-icdrelay1.mx.pearson.com. NS
Answer
The response has no answer records.
Authority
pearson.com. 900 SOA dns-amer-2.ptns.pearson.com. gns-dnsoperations.pearson.com. 2013052619 900 900 2592000 900
Additional
. 0 OPT ; payload 1220, xrcode 0, version 0, flags 0