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

Results for_spf.eemsg5.mail.mil

Resolver

Location

TXT

Name	TTL	Value
_spf.eemsg5.mail.mil	912	spf2.0/pra ip4:140.17.113.224/27 ip4:140.17.137.224/27 ip4:140.17.145.224/27 ip4:140.17.27.224/27 -all
_spf.eemsg5.mail.mil	912	v=spf1 ip4:140.17.113.224/27 ip4:140.17.137.224/27 ip4:140.17.145.224/27 ip4:140.17.27.224/27 -all