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

Results forspf3.gcore.lu

Resolver

Location

TXT

Name	TTL	Value
spf3.gcore.lu	300	v=spf1 ip4:185.12.212.22/32 ip4:92.223.1.0/24 ip4:92.223.125.21/32 ip4:92.223.99.99/32 ip4:92.223.104.11/32 ip4:52.169.205.96/32 ip4:92.223.127.228/32 -all