_spf.one.com has no CNAME records.
Question and response
Question
dig _spf.one.com. NS
Answer
The response has no answer records.
Authority
one.com. 293 SOA a.b-one-dns.net. hostmaster.one.com. 2026021901 1800 900 1209600 300
Additional
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0