The deprecation of EWS in Exchange Online starts today. This is a multi-step process, years in the making, and this post has lots of important information. We will keep this post updated if we have new information to add.
The first change, as previously announced, starting early October 2026, means setting EWSEnabled to True will no longer be sufficient on its own to keep EWS working in the tenant: an AppID allow list (EWSAllowedAppIDs) will be required to specify apps that you want to permit access to EWS.
What happens next
Customer tenants in our multi-tenant (WW) cloud
|
EWSEnabled state |
EWSAllowedAppIDs state |
When |
|
True |
Null |
We populated EWSAllowedAppIDs for all such tenants on October 10-11. After October 11, any tenant admin who sets EWSEnabled = True, must populate EWSAllowedAppIDs by themselves. If the tenant is already set to EWSEnabled = True, Microsoft will not make changes to EWS availability until April 2027. |
|
Null |
Null |
Tenants will get a 7-day warning in Message Center to tell them we will populate their EWSAllowedAppIDs (based on 60-day usage) and then set EWSEnabled = False. This process has now started. If EWS gets disabled, tenant admins can temporarily re-enable it by following Exchange Online EWS application stopped working? Do this. | Microsoft Community Hub. |
|
False |
(Any) |
EWS is already disabled by tenant admin; Microsoft will make no changes. |
Multi-tenant WW cloud now requires the presence of EWSAllowedAppIDs if EWSEnabled = True.
Customer tenants in our Sovereign cloud environments
Stay tuned for more detailed timeline.
Other Important Information
Changing Related EWS Settings
Please remember that:
- Changes to EWSAllowedAppIDs take 24 hours to take effect
- Changes to EWSEnabled take typically under 1 hour (but can be up to 4 hours)
- EWSAllowList property does not need to be configured and/or changed (it is not related to EWS deprecation). Please review this blog if unclear.
If EWS gets disabled by Microsoft, only the tenant admin can re-enable it (Microsoft cannot do this). Step-by-step process is described in Exchange Online EWS application stopped working? Do this. | Microsoft Community Hub.
Microsoft Applications EWS Use
We know customers are still seeing traffic from some Microsoft applications. These applications (if they show up in the EWS usage report) still need to be added to the EWSAllowedAppIDs list to keep working.
The latest on each of these:
- Outlook for Windows: Customers should be on latest builds (August 2026 build 16.0.20430.20092 or higher). If customers see problems with EWS disabled, it may be due to customer forced configuration (see this example). We recommend testing to determine if blocking EWS for the Office client AppID is possible in your tenant, without impact. Microsoft successfully disabled EWS internally over a year ago.
- Outlook for Mac: Please update to the latest builds and switch to the new Outlook for Mac. If you are already using new Outlook, then this change will not affect you. If you still need to use Classic Outlook, ensure the “Microsoft Office” AppID is in your EWSAllowedAppIDs list.
- Excel Power Query: Please see https://aka.ms/xlewsretirement.
- PowerBI: we will provide an update soon.
- Exchange Server / Exchange hybrid: please see Impact of Exchange Online EWS Deprecation on Hybrid Rich Coexistence and Cross-org Sharing | Microsoft Community Hub.
Updates to this blog post:
- 10/26/2026: Added a note that clarifies that if the tenant is already set to EWSEnabled = True, Microsoft will not make EWS changes until April 2027.
- 10/21/2026: Updated the post to reflect that EWS disablements have been started and linked to the reference on how to re-enable it.
- 10/15/2026: Updated the table with next steps for WW tenants and reorganized the information for readability.
- 10/2/2026: Mentioned that EWSEnabled settings can have some variability in how quickly they apply (to account for a few occurances we have seen).
The Exchange Team
