mumu.tierpoint.com has no NS records.
NS records for this zone are defined at tierpoint.com.
NS records for this zone are defined at tierpoint.com.
Question and response
Question
dig mumu.tierpoint.com. NS
Answer
The response has no answer records.
Authority
tierpoint.com. 300 SOA ns1.tierpoint.com. domains.tierpoint.com. 2017138521 10800 3600 2419200 300
Additional
. 0 OPT ; payload 1220, xrcode 0, version 0, flags 0