_spf.mx.emailthing.app has no CNAME records.
Question and response
Question
dig _spf.mx.emailthing.app. NS
Answer
The response has no answer records.
Authority
emailthing.app. 1800 SOA brad.ns.cloudflare.com. dns.cloudflare.com. 2398104126 10000 2400 604800 1800
Additional
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0