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

Results forspf3.serverdomain.org

Resolver

Location

TXT

Name	TTL	Value
spf3.serverdomain.org	3600	v=spf1 ip4:78.47.122.108 ip4:88.99.124.251 ip4:78.47.160.127 ip4:159.69.101.180 ip4:88.198.107.26 ip4:88.198.104.178 ip4:159.69.102.119 ip4:5.75.210.16 ip4:5.75.215.54 ip4:5.75.212.93 ip4:116.202.5.110 ip4:88.198.78.10 ip4:5.75.213.241 -all