mail.windmillcache.com has no NS records.
NS records for this zone are defined at windmillcache.com.
NS records for this zone are defined at windmillcache.com.
Question and response
Question
dig mail.windmillcache.com. NS
Answer
The response has no answer records.
Authority
windmillcache.com. 3600 SOA dns.windmillcache.com. hostmaster.windmillcache.com. 1584239809 43200 3600 604800 3600
Additional
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0