mail.asergo.com has no NS records.
NS records for this zone are defined at asergo.com.
NS records for this zone are defined at asergo.com.
Question and response
Question
dig mail.asergo.com. NS
Answer
The response has no answer records.
Authority
asergo.com. 1800 SOA igor.ns.cloudflare.com. dns.cloudflare.com. 2394994056 10000 2400 604800 1800
Additional
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0