mailout05.viacom.com has no NS records.
NS records for this zone are defined at viacom.com.
NS records for this zone are defined at viacom.com.
Question and response
Question
dig mailout05.viacom.com. NS
Answer
The response has no answer records.
Authority
viacom.com. 3600 SOA dns1.p09.nsone.net. hostmaster.nsone.net. 1655182652 600 600 1209600 3600
Additional
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0