Test EWSAllowedAppIDs in Exchange Online

Microsoft is retiring Exchange Web Services (EWS), the older SOAP-based API that applications use to read and write mailbox data in Exchange Online. During the transition window—from phased disablement in October 2026 until full retirement on April 1, 2027—EWSAllowedAppIDs is the temporary gatekeeper: a tenant-wide list of Microsoft Entra application IDs (the client IDs of app registrations) that may still call EWS when you set EwsEnabled to $true. Only listed apps keep access while you migrate; after April 2027, the list no longer matters because EWS is blocked outright. This article shows how to test that gate before you depend on it.
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https://4sysops.com/archives/test-ewsallowedappids-in-exchange-online/