mail3.sendershub.com has no NS records.
NS records for this zone are defined at sendershub.com.
NS records for this zone are defined at sendershub.com.
Question and response
Question
dig mail3.sendershub.com. NS
Answer
The response has no answer records.
Authority
sendershub.com. 1800 SOA clay.ns.cloudflare.com. dns.cloudflare.com. 2397823761 10000 2400 604800 1800
Additional
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0