lb1.dub.prod.101domain.com has no MX records.
Question and response
Question
dig lb1.dub.prod.101domain.com. MX
Answer
The response has no answer records.
Authority
prod.101domain.com. 38400 SOA NS1.FASTTRACKDNS.com. ADMIN.prod.101domain.com. 2015126960 10800 3600 604800 38400
Additional
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0