How do authentication failures affect DMARC aggregate scores?

Your DMARC aggregate reports are essentially scorecards. For every source that sends email using your domain, the report tracks how many messages passed and failed, broken down by SPF result, DKIM result, and alignment.

Authentication failures show up as failing rows in the report. The key metric to watch is the pass rate: what percentage of messages from each source are fully passing DMARC. A high failure rate from a specific source tells you something's misconfigured for that sender.

Here's the important nuance: DMARC's policy determines what actually happens to failing messages. If you're at p=none, failures are logged but no action is taken. If you're at p=quarantine or p=reject, failures affect delivery. So while failures at p=none don't hurt deliverability directly, they're a signal that misconfigured senders exist and would cause delivery problems if you tighten the policy.

You can also see failures broken down by source IP and sending domain, which helps identify exactly which ESP or mail server is the source of the problem. Common culprits: third-party senders whose DKIM signing isn't aligned with your domain, or ESPs using their own envelope senders for SPF without your domain in the path.

Reading raw DMARC XML reports is not fun. Our free Review My Emails DMARC Parser translates them into readable output. If your failure rates are high and you're not sure why, that's a good place to start.