PSA: Apple Mail on Mac may lose Microsoft 365 sync as EWS turns off
Microsoft began disabling Exchange Web Services in Exchange Online on October 1, 2026 — the protocol Apple Mail, Calendar, Contacts, Notes, and Reminders on Mac still use for Microsoft 365. Apple’s Graph API update for macOS 27 has not shipped yet.
Microsoft began disabling Exchange Web Services (EWS) by default in Exchange Online on October 1, 2026 — a cutover that can break sync for Apple Mail, Calendar, Contacts, Notes, and Reminders on Mac when those apps talk to Microsoft 365 work accounts, MacRumors reports (Tim Hardwick, October 1, 2026).
Apple’s built-in Mac clients still rely on EWS for Exchange Online. iPhone and iPad Mail are not in the same boat: they use Exchange ActiveSync instead. On-premises Exchange Server is also unaffected — Microsoft’s retirement applies to cloud-hosted Exchange Online / Microsoft 365 only.
What Microsoft is doing
In its Exchange Team Blog (updated September 9, 2026), Microsoft describes a phased disablement:
- Starting October 1, 2026: tenants that still have
EWSEnabledset to the default (Null) see that value flipped toFalseas the rollout lands, blocking EWS unless admins re-enable it. - Organizations that already set
EWSEnabled=Trueand maintain an AppID allow list can keep selected EWS apps running for now. - April 1, 2027: EWS in Exchange Online is scheduled for a permanent shutdown — Microsoft says no extensions are planned.
Because the October change is phased, some Mac users may lose sync sooner than others. Campus and enterprise IT notes already describe Apple Mail failing with account errors when a tenant turns EWS off early.
Where Apple stands
Apple’s Platform Deployment guide for Microsoft Exchange states that Apple is “actively working with Microsoft” to move Mail, Calendar, Contacts, Notes, and Reminders to the Microsoft Graph API in a future macOS 27 update, including declarative device-management configuration.
That Graph-backed update has not shipped. MacRumors notes Apple skipped macOS 27.1 betas entirely, and public release notes for the macOS 27.2 betas have not mentioned Graph support yet.
What Mac users and IT can do now
- Ask IT whether EWS is still enabled for your Microsoft 365 tenant (or whether Apple Mail’s AppID sits on an allow list).
- Switch to a Graph-ready client such as Outlook for Mac or Outlook on the web if Mail/Calendar stop syncing.
- Do not expect iPhone/iPad Mail to break from this specific EWS cutover — those platforms use ActiveSync.
- Keep macOS current; when Apple ships the Graph migration, it is the durable fix for the built-in apps.
If you are also catching up on Mac security releases, see our separate note on the CoreGraphics CVE-2026-86950 public crash PoC.
Do you use Apple Mail on Mac with a Microsoft 365 work account?
Yes — and sync still works today0 votes0%
Yes — and sync already broke0 votes0%
I switched to Outlook for Mac0 votes0%
No Microsoft 365 on my Mac0 votes0%
0 votesPoll closed
Bottom line: October 1, 2026 is the start of Microsoft’s default EWS off-switch in Exchange Online. Until Apple lands Graph support in a future macOS 27 update, Mac users who depend on Apple Mail for Microsoft 365 should confirm IT exceptions — or move to Outlook.
Sources: MacRumors — Tim Hardwick (Oct. 1, 2026); Microsoft Exchange Team — Exchange Online EWS, Your Time is Almost Up (updated Sept. 9, 2026); Apple — Integrate with Microsoft Exchange; heise online.