reply.s51.exacttarget.com has no NS records.
NS records for this zone are defined at s51.exacttarget.com.
NS records for this zone are defined at s51.exacttarget.com.
Question and response
Question
dig reply.s51.exacttarget.com. NS
Answer
The response has no answer records.
Authority
s51.exacttarget.com. 300 SOA dns1.p01.nsone.net. hostmaster.nsone.net. 1679951115 7200 3600 1209600 3600
Additional
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0