There are two tactics to apply different DMARC policies for the main domain and subdomains:
1. Publish a DMARC record for a subdomain and specify the policy level you require.
2. Use the sp= tag on your parent domain’s DMARC record to specify what policy level you would like your subdomains to have, rather than inheriting it from the parent domain. In this case, a full record example would look like the following:
v=DMARC1; p=reject; sp=none; fo=1; rua=mailto……..
In GlockApps DMARC Analyzer, you can specify a different DMARC policy for the subdomains and the tool will include the sp= tag with the specified policy in the DMARC record.
Read also: Why Every Business Needs DMARC