spf.rocketseed.com has no CNAME records.
Question and response
Question
dig spf.rocketseed.com. NS
Answer
The response has no answer records.
Authority
rocketseed.com. 600 SOA pdns05.domaincontrol.com. dns.jomax.net. 2026021000 28800 7200 604800 600
Additional
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0