tracking.acumbamail.com has no NS records.
NS records for this zone are defined at acumbamail.com.
NS records for this zone are defined at acumbamail.com.
Question and response
Question
dig tracking.acumbamail.com. NS
Answer
The response has no answer records.
Authority
acumbamail.com. 180 SOA ns10.dnsmadeeasy.com. dns.dnsmadeeasy.com. 2009010712 43200 3600 1209600 180
Additional
. 0 OPT ; payload 1280, xrcode 0, version 0, flags 0