internalmx.smtpcorp.com has no TXT records.
Question and response
Question
dig internalmx.smtpcorp.com. TXT
Answer
The response has no answer records.
Authority
smtpcorp.com. 1800 SOA ada.ns.cloudflare.com. dns.cloudflare.com. 2397629858 10000 2400 604800 1800
Additional
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0