smtp.prod.ruby.multimediabs.com has no CNAME records.
Question and response
Question
dig smtp.prod.ruby.multimediabs.com. NS
Answer
The response has no answer records.
Authority
ruby.multimediabs.com. 69 SOA ns1.prod-cloud-ocb.orange-business.com. fe-ruby\.oab.orange.com. 1 7200 900 1209600 300
Additional
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0