sender1.acmbma.com has no NS records.
NS records for this zone are defined at acmbma.com.
NS records for this zone are defined at acmbma.com.
Question and response
Question
dig sender1.acmbma.com. NS
Answer
The response has no answer records.
Authority
acmbma.com. 180 SOA ns0.dnsmadeeasy.com. dns.dnsmadeeasy.com. 2008010183 43200 3600 1209600 180
Additional
. 0 OPT ; payload 1280, xrcode 0, version 0, flags 0