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

Results forspf-b.outlook.com

Resolver

Location

TXT

Name	TTL	Value
spf-b.outlook.com	300	v=spf1 ip4:65.55.78.128/25 ip4:111.221.112.0/21 ip4:207.46.58.128/25 ip4:111.221.69.128/25 ip4:111.221.66.0/25 ip4:111.221.23.128/25 ip4:70.37.151.128/25 ip4:157.56.248.0/21 ip4:213.199.177.0/26 ip4:157.55.225.0/25 ip4:157.55.11.0/25 -all