spf.outbound.mailhostbox.com has no CNAME records.
Question and response
Question
dig spf.outbound.mailhostbox.com. NS
Answer
The response has no answer records.
Authority
mailhostbox.com. 1743 SOA andy.ns.cloudflare.com. dns.cloudflare.com. 2397701592 10000 2400 604800 1800
Additional
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0