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

Results for_u.nic.io._spf.smart.ondmarc.com

Resolver

Location

TXT

Name	TTL	Value
_u.nic.io._spf.smart.ondmarc.com	3600	v=spf1 ip4:74.125.0.0/16 ip4:148.105.0.0/16 ip4:209.85.128.0/17 ip4:198.2.128.0/18 ip4:23.83.208.0/20 ip4:205.201.128.0/20 ip4:208.76.24.0/22 ip4:34.82.162.0/24 ip4:35.227.130.0/24 ip4:70.33.209.0/24 ip4:50.31.33.140/31 ip4:87.252.221.246/31 ip6:2001:48 60:4000::/36 ip6:2404:6800:4000::/36 ip6:2607:f8b0:4000::/36 ip6:2800:3f0:4000::/36 include:_p.1.s7wbes._u.nic.io._spf.smart.ondmarc.com ~all