Exchange Web Services (EWS) retirement in Exchange Online is entering its final phase. Over the last several years, Microsoft has worked with product teams, independent software vendors (ISVs), and c...
Updated Aug 21, 2026
Version 12.0
Blog Post
7 MIN READ
Introducing EWSAllowedAppIDs: Preparing for the Final Phase of EWS Retirement
One question MC1446796 - Migrate Free/Busy, MailTips, and Calendar Sharing before EWS deprecation
Yesterday we got the information in MC that FreeBusy via OrgRelationships is also affected by the EWS deprecation staring with 1st october.
Because orgrelationships, sharingpolicies and availabilityaddressspaces in EXO are also EWS-based.
If we need more time to migrate from OrgRelationships to CrossTenantAccessPolicies, we should follow the guidance of the latest blog we published: https://techcommunity.microsoft.com/blog/exchange/exchange-online-ews-your-time-is-almost-up/4492361
We only have this single UseCase (OrgRelationships / FreeBusy) to extend EWS Usage.
Which ApplicationID do I have to put on the EwsAllowList?
Greg Taylor - EXCHANGE
Microsoft
MicrosoftYou don't need to put any AppIDs into the list to keep using the legacy method - that method doesn't use OAuth. if EWSEnabled is set to True, we'll let that traffic keep working, we will manage that.