mx-dfw.automattic.com has no CNAME records.
Question and response
Question
dig mx-dfw.automattic.com. NS
Answer
The response has no answer records.
Authority
automattic.com. 60 SOA ns1.automattic.com. hostmaster.automattic.com. 2023091834 14400 7200 604800 60
Additional
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0