mailsorter.sb.monster.com has no NS records.
NS records for this zone are defined at monster.com.
NS records for this zone are defined at monster.com.
Question and response
Question
dig mailsorter.sb.monster.com. NS
Answer
The response has no answer records.
Authority
monster.com. 600 SOA ns1.tmpw.net. hostmaster.tmpw.net. 1771829403 1800 600 604800 86400
Additional
The response has no additional records.