rdumail1.benefitfocus.com has no CNAME records.
Question and response
Question
dig rdumail1.benefitfocus.com. NS
Answer
The response has no answer records.
Authority
benefitfocus.com. 1800 SOA damiete.ns.cloudflare.com. dns.cloudflare.com. 2398078867 10000 2400 604800 1800
Additional
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0