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

Results forspf3.septacode.com

Resolver

Location

TXT

Name	TTL	Value
spf3.septacode.com	1800	v=spf1 ip4:198.244.60.0/22 ip4:198.37.144.0/20 ip4:198.61.254.0/23 ip4:204.220.160.0/21 ip4:204.220.168.0/21 ip4:204.220.176.0/20 ip4:208.117.48.0/20 ip4:209.61.151.0/24 ip4:209.85.128.0/17 ip4:223.165.113.0/24 include:spf4.septacode.com ~all