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Updated Oct 27, 2026
Version 21.0
Blog Post
I'm currently catching up with the M365 Message Centre after returning from leave and have seen an update to this EWS retirement under MC1447678 published on 24/08/2026.
This states:
2.Create and validate an allow list
Create an EWSAllowedAppIDs allow list containing applications that must continue using EWS.
Important considerations:
- Applications appearing in EWS usage reports that you intend to continue using should be included in the allow list.
- Microsoft first-party applications that continue to rely on EWS must also be included if they appear in your usage reporting.
- Setting EWSAllowedAppIDs replaces the existing list. Ensure all required App IDs are included when updating the configuration.
I find this statement alarming:
- Microsoft first-party applications that continue to rely on EWS must also be included if they appear in your usage reporting.
Shouldn't Microsoft have finished updating their own applications before starting to enforce this? And if not why is it up to individual tenants to allow these to prevent disruption?
I was under the impression that reported Microsoft first party applications being reported in the EWS usage report could be ignored as it was Microsoft's responsibility to update these before the deadline.
The required application being reported as still using EWS is Microsoft Office (d3590ed6-52b3-4102-aeff-aad2292ab01c), so please can you clarify that the official position is that I will need to add this to the EWSAllowedAppIDs allow list in my tenant so this continues to work after 1st October?
Teams and New Outlook are still dependant so I wouldn't hold your breath.
- Greg Taylor - EXCHANGE
Microsoft
Not quite true JL-MDM . New Outlook has no EWS dependency at all. Teams Middle Tier does, but they'll have that addressed by Oct.
owainwtb - Old versions of Outlook still use EWS. We're leaving it down to you to decide if you want to keep EWS enabled in case you can't update in time. If you have Outlook updated across the board, you shouldn't see EWS usage. I've had EWS disabled on my mailbox for 18 months and use Outlook all day every day, and I haven't seen any issues whatsoever, since it was updated to stop using EWS for things like MailTips.
So any appID that appears in your EWS Usage report, needs to be added to the list if you want to keep using it.
Greg Taylor - EXCHANGE Could you clarify when you say "if you have Outlook updated across the board" whether you mean specifically only New Outlook and not Outlook (classic), or if that includes up-to-date, fully supported versions of Outlook (classic)?
Also, is d3590ed6-52b3-4102-aeff-aad2292ab01c used by both Outlook and Teams Middle Tier? d3590ed6-52b3-4102-aeff-aad2292ab01c seems to cover a lot of ground, and it's hard to pinpoint what exactly is generating it (and according to the EWS Usage report, all at 5 am, once per week).
Thank you for your help!
