MailStore – How to re-enable Exchange Online EWS
ID: 16394
Summary
Microsoft disables EWS.
Cause
Microsoft will begin disabling EWS on October 1st, 2026.
Resolution
If you still need to use EWS, you will have two choices:
Set EWSEnabled to True and maintain an AppID Allow List (via Baseline Security Mode or Exchange Online PowerShell).
Set EWSEnabled back to Null, which re-enables EWS without restrictions until the final deprecation occurs. This will have to be done using Exchange Online PowerShell.
Please refer to the Microsoft Tech Community article for details:
https://techcommunity.microsoft.com/blog/exchange/exchange-online-ews-your-time-is-almost-up/4492361
Third-Party Issue
This is a third-party issue and cannot be resolved by MailStore.