smtp.prp.ruby.multimediabs.com has no NS records.
NS records for this zone are defined at ruby.multimediabs.com.
NS records for this zone are defined at ruby.multimediabs.com.
Question and response
Question
dig smtp.prp.ruby.multimediabs.com. NS
Answer
The response has no answer records.
Authority
ruby.multimediabs.com. 300 SOA ns1.prod-cloud-ocb.orange-business.com. fe-ruby\.oab.orange.com. 1 7200 900 1209600 300
Additional
. 0 OPT ; payload 1280, xrcode 0, version 0, flags 0