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

Results for_spf.topicus.nl

Resolver

Location

TXT

Name	TTL	Value
_spf.topicus.nl	3600	v=spf1 ip4:195.35.227.56/29 ip4:195.35.227.192/28 ip4:195.35.231.128/26 ip4:195.35.228.224/30 ip4:84.241.175.50 ip4:31.7.7.78 ip4:185.144.224.111 ip4:185.104.101.134 ip4:185.144.224.30 ip4:80.65.96.45 ip4:89.221.178.154 ip4:157.97.113.166 ip4:37.97.241.71 include:spf.protection.outlook.com -all