Apple Mail EWS sync intermittent after EwsEnabled=True + AppID allow list

Because another mailbox and Mac continue working, this does not establish a tenant-wide EWS interruption. Microsoft does not document a tenant-side flag that identifies a specific mailbox as part of disruption testing, or a macOS-version matrix for EWS session behavior. Compare the affected mailbox with the working one using the mailbox-level EWS setting, then retrieve the organization’s effective allowed application IDs and confirm Apple Internet Accounts is present. Correlate each failure with Microsoft 365 service health, Microsoft Entra sign-in logs, and Conditional Access results. The EWS usage report confirms successful SOAP activity and last activity, but it is aggregated and not a complete failure trace. Exchange Online does not expose custom throttling-policy cmdlets, so there is no supported per-mailbox adjustment. Update macOS, reproduce in a clean user profile, and record UTC timestamps. If authentication succeeds but EWS activity stops, provide the evidence to Microsoft support and Apple.