MacHabitsIf Apple Mail or Calendar on your Mac suddenly stopped syncing a work email account around the start of October 2026, this is not a macOS bug, and reinstalling, resetting preferences, or waiting for a point update will not fix it. Microsoft turned off the protocol that connects Apple Mail to Microsoft 365 work accounts, on a schedule it announced back in 2023. Here is exactly what happened and what your real options are.
What actually happened on October 1
On October 1, 2026, Microsoft began disabling Exchange Web Services (EWS) by default in Exchange Online. EWS is the protocol Apple's Mail and Calendar apps on Mac have relied on for years to connect to Microsoft 365 work and school accounts. Microsoft stopped adding new features to EWS back in 2018, announced in 2023 that it would disable the protocol in Exchange Online starting October 2026, and has now begun doing exactly that.
The shutdown is not instant or universal for every tenant on the same day; Microsoft is rolling it out in phases rather than flipping a single global switch. If your account hasn't been affected yet, it may simply not have reached your organization's tenant in the rollout order.
Who is affected
- Apple Mail and Calendar on Mac, when connected to a Microsoft 365 or Exchange Online work or school account, specifically.
- Legacy Outlook for Mac is affected even more severely. Unlike Apple Mail, legacy Outlook for Mac is explicitly excluded from Microsoft's administrative allowlist exceptions, meaning IT admins cannot grant it an extension the way they can for other apps.
- Any in-house or departmental software that connects directly to Exchange Online using EWS.
Who is not affected
- Organizations running their own on-premises Exchange Server are not affected at all; this change is specific to Exchange Online (the cloud-hosted Microsoft 365 version), not Exchange in general. On-premises Exchange will continue supporting EWS for Outlook for Mac clients until October 2029.
- iPhone and iPad Mail are unaffected, since iOS and iPadOS use a different protocol, Exchange ActiveSync, rather than EWS.
- Organizations that have explicitly kept EWS enabled through their own configuration are unaffected for now, through a transition window described below.
- Current Outlook for Mac (sometimes called "new Outlook," distinct from "legacy Outlook for Mac") uses Microsoft Graph rather than EWS and is unaffected by this specific change.
Check whether you are affected
- Open Apple Mail and check whether your Microsoft 365 work account shows a sync error, stops receiving new mail, or shows a connection warning specifically for that account.
- Check whether the same account syncs correctly in current Outlook for Mac or Outlook on the web. If it works there but not in Apple Mail, that confirms this is the EWS cutoff rather than a credentials or network problem.
- If you're the IT admin for your organization, or can ask one, confirm whether your Exchange Online tenant has EWS explicitly enabled or disabled.
Option 1: ask your IT admin to re-enable EWS
This is the fastest fix if your organization controls its own Microsoft 365 tenant, and it buys real time, not just a short delay:
- Through March 31, 2027, administrators can selectively re-enable EWS access via Exchange Online PowerShell, using an allowlist of specific permitted application IDs.
- This option does not cover legacy Outlook for Mac specifically. Microsoft excludes it from the administrative exception list entirely, so re-enabling EWS for your tenant restores Apple Mail and other EWS-based tools, but will not bring back legacy Outlook for Mac.
- Admins who want this option need to have set the
EWSEnabledconfiguration correctly before the cutoff; if your tenant missed that window, check with Microsoft's current documentation on whether re-enabling after the fact is still possible for your case.
If you don't manage your own Microsoft 365 environment, ask your IT department specifically about "the EWS deprecation affecting Apple Mail" rather than describing only the symptom; this is a known, named issue on Microsoft's side, and most IT teams following Microsoft's own communications will recognize it immediately.
Option 2: switch to new Outlook for Mac
If your organization isn't going to re-enable EWS, or has already explicitly declined to, switching your mail client is the straightforward path:
- If you currently use legacy Outlook for Mac, Microsoft provides a toggle in the upper-right corner of the app to switch to the current, Graph-based Outlook for Mac experience. Legacy Outlook for Mac stops working against Exchange Online regardless of admin settings, so this switch isn't optional if you want to keep using an Outlook client.
- If you use Apple Mail and your organization has confirmed it will not re-enable EWS, moving that account to Outlook for Mac or Outlook on the web avoids the issue entirely, since both use Microsoft Graph rather than EWS.
Be aware that current Outlook for Mac is a genuinely different experience from Apple Mail or legacy Outlook, and some users report it's missing features both of those offered. If you're attached to Apple Mail's interface specifically, this is a real trade-off, not a drop-in replacement.
Option 3: wait for Apple to add Graph support
The long-term fix would be Apple updating Mail and Calendar to speak Microsoft Graph instead of, or alongside, EWS. As of this writing, Apple skipped a macOS 27.1 release entirely, and the macOS 27.2 beta's release notes make no mention of Graph support being added. There is no announced timeline for Apple to address this on its own, and reporting on the situation describes the relationship between Apple and Microsoft here as lacking the kind of joint roadmap that would make a fast fix likely. If your account must keep working, waiting on Apple is not currently a realistic short-term option.
The full timeline
| Date | What happens |
|---|---|
| 2018 | Microsoft stops adding new features to EWS |
| 2023 | Microsoft announces EWS will be disabled in Exchange Online starting October 2026 |
| October 1, 2026 | EWS begins being disabled by default in Exchange Online, rolled out in phases |
| Through March 31, 2027 | Admins can selectively re-enable EWS via PowerShell allowlist, except for legacy Outlook for Mac |
| April 1, 2027 | Microsoft plans to shut down EWS in Exchange Online permanently, with no extensions currently planned |
| October 9, 2029 | Legacy Outlook for Mac continues working against on-premises Exchange only, not Exchange Online |
The short version
- Microsoft began disabling Exchange Web Services in Exchange Online on October 1, 2026, cutting off the protocol Apple Mail and Calendar use for Microsoft 365 work accounts. This is unrelated to macOS 27 or any Apple update.
- Legacy Outlook for Mac is hit hardest and cannot be exempted by IT admins at all; current Outlook for Mac is unaffected since it uses Microsoft Graph.
- If your organization controls its own tenant, re-enabling EWS through March 2027 is the fastest fix for Apple Mail specifically.
- Apple has not announced Graph support for Mail or Calendar, and nothing in the 27.2 beta suggests it's imminent.