spf.jetsmtp.net has no CNAME records.
Question and response
Question
dig spf.jetsmtp.net. NS
Answer
The response has no answer records.
Authority
jetsmtp.net. 253 SOA melina.ns.cloudflare.com. dns.cloudflare.com. 2396931151 10000 2400 604800 1800
Additional
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0