o1.ptr764.billtrust.com has no NS records.
NS records for this zone are defined at billtrust.com.
NS records for this zone are defined at billtrust.com.
Question and response
Question
dig o1.ptr764.billtrust.com. NS
Answer
The response has no answer records.
Authority
billtrust.com. 180 SOA ns20.digicertdns.com. dns.digicertdns.com. 2009014643 43200 3600 1209600 180
Additional
. 0 OPT ; payload 1280, xrcode 0, version 0, flags 0