A user on a small Microsoft 365 Business tenant experiences intermittent email syncing issues with Apple Mail on macOS, despite a healthy connection displayed by Connection Doctor. New mail appears on the user's iPhone/iPad via ActiveSync but not on their Mac. This problem recurs every 1-3 days, even after temporary resolutions.Troubleshooting steps included verifying autodiscover, enabling EWS at the mailbox and organization levels, and configuring EwsAllowedAppIDs for Apple. The Mac Mail account was fully re-added, and network-related factors were ruled out.A second mailbox on the same tenant, using Apple Mail on a different Mac, does not exhibit this issue, suggesting it's not a tenant-wide problem. The user speculates if the issue is related to Microsoft's ongoing EWS disruption testing or differences in EWS handling between macOS versions.The user also seeks advice on additional tenant-side checks, such as throttling policies, CAS mailbox settings, or conditional access rules, that might apply per-mailbox. They are willing to provide diagnostic data to help resolve the problem before EWS is phased out.