mail1.xcastlabs.com has no NS records.
NS records for this zone are defined at xcastlabs.com.
NS records for this zone are defined at xcastlabs.com.
Question and response
Question
dig mail1.xcastlabs.com. NS
Answer
The response has no answer records.
Authority
xcastlabs.com. 1800 SOA dan.ns.cloudflare.com. dns.cloudflare.com. 2398240070 10000 2400 604800 1800
Additional
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0