mail.doximapps.com has no NS records.
NS records for this zone are defined at doximapps.com.
NS records for this zone are defined at doximapps.com.
Question and response
Question
dig mail.doximapps.com. NS
Answer
The response has no answer records.
Authority
doximapps.com. 1800 SOA ivan.ns.cloudflare.com. dns.cloudflare.com. 2398586976 10000 2400 604800 1800
Additional
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0