mail.domain-holding.co.uk has no NS records.
NS records for this zone are defined at domain-holding.co.uk.
NS records for this zone are defined at domain-holding.co.uk.
Question and response
Question
dig mail.domain-holding.co.uk. NS
Answer
The response has no answer records.
Authority
domain-holding.co.uk. 86400 SOA ns-fh.ui-dns.co.uk. dnsadmin.ionos.com. 28 10800 172800 1209600 86400
Additional
. 0 OPT ; payload 1220, xrcode 0, version 0, flags 0