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

Results forspf3.ustsg.com

Resolver

Location

TXT

Name	TTL	Value
spf3.ustsg.com	300	v=spf1 ip4:165.173.128.0/24 ip4:135.84.82.0/24 ip4:136.143.161.0/24 ip4:207.99.114.4 +ip4:192.185.4.131 +ip4:68.66.226.100 ip6:2607:13c0:0001:0000:0000:0000:0000:7000/116 ip6:2607:13c0:0002:0000:0000:0000:0000:1000/116 ~all