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

Results forspf.smartemailing.cz

Resolver

Location

TXT

Name	TTL	Value
spf.smartemailing.cz	7200	v=spf1 ip4:193.19.178.128/27 ip4:193.19.178.159 ip4:193.19.178.162 ip4:37.46.82.0/28 ip4:130.193.9.208/28 ip4:130.193.12.56 ip4:193.19.178.96/27 ip4:37.46.82.240/28 ip4:45.76.88.183 ip4:45.77.53.19 ip4:104.207.131.63 include:spf1.smartemailing.cz ~all