Mail you send to @icloud.com or @me.com addresses bounces with “554 5.7.1 … rejected due to DMARC policy” (some servers show 550 instead of 554).
iCloud returns 5.7.1 when the visible From domain fails DMARC and that domain publishes an enforcing policy (quarantine or reject) — meaning neither SPF nor DKIM aligned with your From domain for that message. A frequent trap appears right after someone “sets up DMARC”: the Return-Path (MAIL FROM) subdomain their sending service uses doesn't resolve — an NXDOMAIN — which makes SPF fail, and with no aligned DKIM to fall back on, DMARC fails at iCloud specifically because iCloud enforces alignment strictly. Source: Apple Support — If your email is marked as spam or bounced (102322) · verified 2026-07-18.
p=none, fix alignment, then re-tighten.It's about your domain's authentication, not the recipient's mailbox. A “5.7.1 rejected due to DMARC policy” message means your own From domain failed DMARC and publishes an enforcing policy — so the fix is on your DNS and sending configuration, not the recipient's side.
You can open one by hand — they're just XML — but they're designed to be machine-read. A monitoring tool that names each source IP in plain English and tracks pass rates over time is what makes them useful week to week, instead of decoding gzip XML every day.
DNS changes propagate within a few hours (up to 48h). For anything you diagnose from aggregate reports, new reports arrive daily, so allow a day or two to confirm a source now passes and aligns.