Overview
- On October 1, 2026, tenants with EWSEnabled set to Null will have it changed to False, blocking all EWS calls unless admins acted in advance.
- Tenants that set EWSEnabled=True and configure an AppID Allow List by the end of August 2026 will avoid the automatic block, and from October only allow‑listed apps can use EWS.
- Microsoft will pre-populate allow lists in September 2026 for customers who do not create their own, and may run brief “scream tests” and send monthly Message Center usage summaries before the cutoff.
- EWS in Exchange Online will be permanently disabled on April 1, 2027, at which point admin controls will be removed and no exceptions will be granted.
- On‑premises Exchange is not affected, but hybrid customers must move cloud mailboxes to Graph and use Exchange SE for Graph calls to Exchange Online.