tracking.heysender.com has no NS records.
NS records for this zone are defined at heysender.com.
NS records for this zone are defined at heysender.com.
Question and response
Question
dig gasmtp001-ams-lw.ubivox.net. NS
Answer
The response has no answer records.
Authority
ubivox.net. 600 SOA pns31.cloudns.net. hostmaster.ubivox.com. 365 14400 7200 2419200 600
Additional
. 0 OPT ; payload 4096, xrcode 0, version 0, flags 0