If anyone in your business reads work email on a Mac using Apple’s built-in Mail app, it may soon stop syncing. Microsoft has started switching off an old connection method called Exchange Web Services (EWS), and Apple’s Mac apps still rely on it for Microsoft 365 accounts.
What’s happened
Microsoft announced back in 2023 that it would retire EWS in Exchange Online, the email part of Microsoft 365. On 1 October 2026 it started switching it off: Microsoft 365 organisations that haven’t made a choice have the setting changed to “off”. EWS will be switched off permanently on 1 April 2027, and Microsoft says there will be no exceptions.
Until then, an administrator can switch EWS back on and approve the specific apps that still need it. Anything not on the approved list is blocked.
Apple’s Mail, Calendar, Contacts, Notes and Reminders apps on the Mac still use EWS for Microsoft 365 accounts. Apple says it is working with Microsoft to move them to Microsoft’s newer connection method, Microsoft Graph, in a future update to macOS 27, but there’s no date yet. iPhones and iPads connect a different way and aren’t affected, and Microsoft’s own Outlook app for Mac already uses the newer method.
Other software can be caught out too. Older backup, archiving, CRM and scan-to-email tools sometimes connect to mailboxes using EWS.
What it means for your business
Once EWS is switched off for your Microsoft 365 account, a Mac user on Apple Mail may find that new emails and calendar invites simply stop arriving, often without an obvious error. That’s easy to miss for days, and it tends to surface as a missed client email or meeting.
Microsoft only started switching EWS off on 1 October and is working through organisations, so the change may not have reached your business yet. That makes now a good time to check, rather than waiting for someone to notice their inbox has gone quiet.
What to do now
- Find out what still uses EWS. The Microsoft 365 admin centre has an EWS usage report showing which apps connect this way.
- Move Mac users to Outlook for Mac, which works with Microsoft 365 without EWS. It’s included with Microsoft 365 business plans that come with the desktop apps.
- If you need Apple Mail for now, your administrator can switch EWS back on and allow it, but treat that as a stop-gap. It ends for good on 1 April 2027.
- Ask your software suppliers whether anything that reads your mailboxes, such as backup, archiving, CRM or scan-to-email, uses EWS and when they’ll move off it.
Sources
- The Register: Exchange Web Services enters the final stretch (1 October 2026)
- MacRumors: Apple Mail on Mac may stop syncing Microsoft 365 work accounts (2 October 2026)
- Office Watch: October 2026 Office changes (22 September 2026)
Details are correct at the time of writing. Check the sources above for any later changes.
Want us to check this for your business? Call 01787 209 003, see our Microsoft 365 and Google Workspace service, or book a free IT consultation.