It can be anything! An apex, subdomain, or even a URL.

Results forspfus.rocketseed.com

Resolver

Location

TXT

Name	TTL	Value
spfus.rocketseed.com	600	v=spf1 ip4:199.48.102.163 ip4:67.22.127.8 ip4:212.54.146.0/24 ip4:212.54.152.0/24 ip4:212.54.155.0/24 ip4:35.209.183.29 ip4:52.144.51.0/24 ip4:52.144.51.77 ip4:212.54.146.15 ~all