The best way to make an analysis of DMARC is to use a third-party processing/reporting service such as DMARC - OnDMARC - Actively block phishing which would receive the reports, process and present them to you in a meaningful way. From there the tool will walk you through the steps that you need to take in order to identify all of your legitimate services and help you configure them correctly with SPF and DKIM. 

Once all of your services are fully configured you will be able to change your DMARC policy to quarantine or reject and stop spoofing or phishing emails that are impersonating your domain or subdomains.

At this stage you will be increasing your deliverability and security and in turn protecting your customers or clients from receiving emails that are from illegitimate sources that you have not authorized.

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