mx1.donweb.com has no NS records.
NS records for this zone are defined at donweb.com.
NS records for this zone are defined at donweb.com.
Question and response
Question
dig mx1.donweb.com. NS
Answer
The response has no answer records.
Authority
donweb.com. 1800 SOA carol.ns.cloudflare.com. dns.cloudflare.com. 2396152988 10000 2400 604800 1800
Additional
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0