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

Results forwww._u.ondmarc.com._spf.smart.ondmarc.com

Resolver

Location

TXT

Name	TTL	Value
www._u.ondmarc.com._spf.smart.ondmarc.com	3600	v=spf1 ip4:74.125.0.0/16 ip4:209.85.128.0/17 ip6:2001:4860:4000::/36 ip6:2404:6800:4000::/36 ip6:2607:f8b0:4000::/36 ip6:2800:3f0:4000::/36 ip6:2a00:1450:4000::/36 ip6:2c0f:fb50:4000::/36 ~all