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

Results forspf1.spf.atom.com

Resolver

Location

TXT

Name	TTL	Value
spf1.spf.atom.com	300	v=spf1 ip6:2c0f:fb50:4000::/36 ip6:2a00:1450:4000::/36 ip6:2800:3f0:4000::/36 ip6:2607:f8b0:4000::/36 ip6:2404:6800:4000::/36 ip6:2001:4860:4000::/36 ip4:87.253.232.0/21 ip4:74.125.0.0/16 ip4:69.72.32.0/20 ip4:23.253.182.0/23 ip4:209.85.128.0/17 ip4:209.6 1.151.0/24 ip4:204.220.160.0/19 include:spf2.spf.atom.com -all