phase 16 implementation

docs/phase16/EMAIL_SENDER_DOMAIN_READINESS_REPORT_v1.0.md

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+# Email Sender-domain Readiness Report
+
+## Decision
+
+**Blocked pending evidence**
+
+Not applicable to the current disabled release state and blocked for any future enablement. No provider, sender domain, SPF, DKIM, DMARC, approved templates, suppression behavior, bounce handling, or owner was supplied.
+
+## Release impact
+
+Launch remains withheld. No exception is accepted.