How to Decode DMARC Aggregate Reports and Act on What They Tell You

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DMARC aggregate reports are daily XML summaries sent by email receivers like Google and Microsoft, showing which IP addresses sent mail claiming to be from your domain and how each message authenticated. Each report follows a standard schema defined in RFC 7489, containing metadata, your published DMARC policy, and individual records grouped by sending source. The key fields to examine are policy_evaluated, which shows whether SPF and DKIM passed with proper alignment, and auth_results, which reveals the raw authentication outcomes before alignment is checked. A source can pass SPF or DKIM in auth_results yet still fail DMARC in policy_evaluated if the authenticating domain does not match the visible From address. Legitimate senders failing alignment should be fixed by configuring proper domain authentication on each platform, while unrecognized sources should be investigated before moving to an enforcing DMARC policy such as p=reject.

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