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

Results for_spf01.mailplug.com

Resolver

Location

TXT

Name	TTL	Value
_spf01.mailplug.com	100	v=spf1 ip4:121.156.118.0/24 ip4:121.156.63.0/24 ip4:220.73.212.0/24 ip4:222.122.219.0/24 ip4:119.206.202.0/24 ip4:223.26.214.0/24 ip4:222.122.189.0/24 ip4:218.145.57.0/24 ~all