mail02.lumaserv.com has no CNAME records.
Question and response
Question
dig mail02.lumaserv.com. NS
Answer
The response has no answer records.
Authority
lumaserv.com. 1800 SOA isla.ns.cloudflare.com. dns.cloudflare.com. 2397856459 10000 2400 604800 1800
Additional
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0