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

Results forspf1.ustsg.com

Resolver

Location

TXT

Name	TTL	Value
spf1.ustsg.com	300	v=spf1 ip4:23.83.208.0/20 ip4:46.232.183.0/24 ip4:199.10.31.235/32 ip4:199.10.31.236/32 ip4:172.255.62.10/32 ip4:172.255.62.11/32 ip4:185.67.193.67/32 ip4:35.85.190.185/32 ip4:8.12.58.0/24 ip4:8.34.161.0/24 ip4:8.224.10.0/24 ip4:213.212.96.64/27 ~all