_spf.spambusters.email has no CNAME records.
Question and response
Question
dig _spf.spambusters.email. NS
Answer
The response has no answer records.
Authority
spambusters.email. 10800 SOA ns1.webhs.org. reports.webhs.pt. 2025120800 86400 7200 3600000 86400
Additional
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0