As customers prepare for the final phase of Exchange Web Services (EWS) retirement in Exchange Online, many are asking the same practical question: how can I prove that EWSAllowedAppIDs is working be...
Updated Sep 09, 2026
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Hi Nino_Bilic
I have few questions regarding this
August vs September: Microsoft mentions configuring EWSAllowedAppIds and EWSEnabled=True by the end of August as optional. Can this be completed during September, provided it is completed before October enforcement? Is there any impact if no action is taken by the end of August? Exchange Online EWS, Your Time is Almost Up | Microsoft Community Hub
Allow List behaviour: If EWSEnabled=True and the Allow List is empty, does EWS remain available to all applications until enforcement? If selected applications are added to the Allow List, will all other applications not included be blocked?
Propagation: Microsoft mentions Allow List changes can take up to 24 hours. Should we wait the full 24 hours before validating the result?
Testing: What is Microsoft's recommended approach for safely testing EWSAllowedAppIds before applying a selective Allow List in production?
Application selection: Should the Allow List include all applications identified through EWS usage reporting, or only applications confirmed to still require EWS?
- Nino_Bilic
Microsoft
- Yes you can do those things in September; we wanted to set a date for folks to get it done before enforcements start in October but there is nothing magical about August as far as this goes.
- If EWSEnabled = True and AppID Allow List is empty, then all EWS apps will be allowed, yes. If AppID allow list is populated then only applications on the list will be allowed (plus cross-tenant free/busy lookups). Other apps (not in the list) woiuld be blocked.
- Yes you should wait for full 24 hours. Yes, it COULD happen faster for you. But if you want this to be predictable, 24 hours.
- Unclear what you mean about question on how to test EWSAllowedAppIDs; this article is about how to test this... right?
- Well... if you see applications in EWS usage reporting, that confirms EWS use, does it not? :) I do not fully understand this question. Bottom line is - unless it is on the AppID Allow List and the Allow List exists, it will be blocked.
- Greg Taylor - EXCHANGE
One thing on this : "If EWSEnabled = True and AppID Allow List is empty, then all EWS apps will be allowed, yes. "
This is only true until Oct 1st. Oct 1st is a hard deadline whereby if the AppID Allow List is empty or missing - EWS will be blocked. Configuring the Allow List is important.
Thanks Nino_Bilic and Greg Taylor - EXCHANGE Appreciate your response.
