DMARC provides some basic policy tags for domain and subdomain

  1. P tag

The use of DMARC's “P" tag is to specify the mail policy that they want to apply on the email message that has failed to pass the DMARC check or it is applied on Top-Domain of the organization and by default on the organization’s subdomain.

example : v=DMARC1; p=quarantine;;; f=0;

Here, P =none applies on the Top-level Domain and by default, it is applicable on the subdomain.

2. sp Tag

By default, the DMARC policy that is set for an organizational domain will be applicable to any subdomains, unless a DMARC record has been published for a specific subdomain. However, domain owners may set separate policies for all subdomains with the “sp” tag (for subdomain policy).

example : v=DMARC1;p=quarantine;sp=none;;; f=0;

Here for Top-level Domain Dmarc policy is Quarantine. and for Sub-Domain DMARC policy is None.