Apple Mail and Microsoft 365: what the end of EWS means for your Mac

Has your work email stopped behaving in Apple Mail on your Mac, while everything still arrives fine on your iPhone? There’s a good chance this is why: Microsoft is switching off Exchange Web Services (EWS) in Exchange Online, the connection Mail, Calendar, Contacts, Notes and Reminders on the Mac use to talk to Microsoft 365. Since 1 October 2026 this has been happening in phases, organisation by organisation, and on 1 April 2027 it shuts down for everyone. This whitepaper covers what’s changing, whether it affects you, what your admin can do and what you can sort out yourself right now.

What’s going on

EWS is an old Exchange interface. Microsoft announced in 2018 that it would get no new features, and in 2023 said it would be switched off in October 2026. After a major security incident in 2024 that plan picked up speed. Its replacement is called Microsoft Graph.

The catch for Mac users: the built-in macOS apps still use EWS for a Microsoft 365 work or school account. Apple says in its deployment documentation that it’s working with Microsoft to move to Graph “in a future update to macOS 27”. There’s no date. As of 13 October 2026 that update hasn’t shipped, and according to MacRumors the release notes for the macOS 27.2 betas haven’t mentioned Graph so far either.

Who is affected

This affects you if all three of these are true:

• You use a Mac with the built-in Mail, Calendar, Contacts, Notes or Reminders apps.
• Your mailbox is hosted in Microsoft 365 (Exchange Online), so a work or school account.
• That account is listed under System Settings > Internet Accounts as an Exchange or Microsoft Exchange account.

Not affected:

• iPhone and iPad. They use Exchange ActiveSync, not EWS.
• Your own Exchange server (on-premises). EWS keeps working there.
• The new Outlook for Mac. It already uses Graph.

Two groups need to pay extra attention. If you still use the old (legacy) Outlook for Mac: according to Microsoft it stops working with Exchange Online from October 2026. And if you’re still on an Intel Mac: macOS 27 only runs on Apple silicon. A Graph update that only comes to macOS 27 will never reach an Intel Mac. Apple hasn’t spelled that out, but it follows from the system requirements.

How to tell it’s happening

• No new mail arrives on the Mac, while your iPhone does have it.
• A small warning triangle shows next to the account in Mail’s sidebar.
• Appointments you make in Outlook or on your phone don’t show up in Calendar on the Mac.
• Connection Doctor sometimes says the login succeeded, but nothing else happens.
• You may get repeated prompts to sign in again.

The tricky part: because Microsoft rolls this out per organisation, it can already be broken for a friend at another company and still fine for you. And sometimes it works for a few days, then stops again.

What your admin can do

Whoever manages your Microsoft 365 environment can keep EWS open for now, but only until 1 April 2027. After that there are no exceptions. Microsoft has put that in writing on Microsoft Learn.

Two settings together decide whether an app can still use EWS:

• EwsEnabled at organisation level. If it’s empty (the default), Microsoft switches it off in phases. According to Microsoft partners you get a Message Center notice seven days before that happens.
• EwsAllowedAppIDs, a list of apps that are still allowed to use EWS. Since 10 October 2026 this list is required: turning EwsEnabled on is no longer enough. That’s in Microsoft notice MC1485116.

For Apple Mail on the Mac, the app ID of Apple Internet Accounts needs to be on that list: f8d98a96-0999-43f5-8af3-69971c7bb423. Admins and Microsoft MVPs widely confirm this ID, but it isn’t in an official Microsoft table. Watch out for three things:

• The list is replaced as a whole every time you change it. Enter only the Apple ID and everything else is gone. Read out the current list first.
• A change to the list can take up to 24 hours to apply. EwsEnabled itself takes about an hour.
• For some organisations Microsoft built the list itself, based on 60 days of usage. Apps you rarely use may be missing.

The Microsoft 365 admin center has an EWS usage report showing which apps still call EWS. Start there.

Other apps that use EWS

It’s not just Apple Mail. Also check:

• Fantastical. Flexibits added a Migrate to Microsoft Graph button under Settings > Accounts. Do it for each Microsoft 365 account and on every device (source).
• Backup tools such as Veeam, Afi, Hornetsecurity and Mimecast. Some already have a Graph version, but Graph doesn’t fully cover archive mailboxes, group mailboxes and public folders yet. Ask your vendor what’s needed.
• Migration tools, CRM integrations, scanners that drop mail into a mailbox, and home-grown scripts. Anything ever built on EWS stops on 1 April 2027.

What you can do yourself now

• Install the new Outlook for Mac. It uses Graph and is in the App Store. Still on the old Outlook? Turn off the Legacy Outlook switch in the app, or update through Help > Check for Updates.
• Use Outlook on the web (outlook.office.com) as a quick fallback. Your mail and calendar are always there.
• Don’t count on IMAP. IMAP only gives you mail, no calendar or contacts, and many organisations have it turned off. I couldn’t confirm whether Apple Mail works reliably with Microsoft 365 over IMAP with modern sign-in.
• Look at alternatives if Outlook isn’t for you. MailMaven and Thunderbird now support Graph. Thunderbird only for mail so far, not yet calendar and contacts.
• Keep macOS up to date. When Apple ships the Graph update, you want it straight away.

For more on Outlook, Teams and Microsoft 365 on the Mac, see the whitepaper Outlook, Teams and Microsoft 365 on the Mac. If you want to manage Macs centrally with Entra ID and Intune, read Apple Business, Entra ID and Intune for small businesses.

Timeline

Step-by-step plan

For the IT contact person

1. Find out who uses a Mac with a Microsoft 365 account in Internet Accounts, and who still runs legacy Outlook for Mac.
2. Run the EWS usage report in the Microsoft 365 admin center and see which apps still use EWS.
3. Check EwsEnabled and EwsAllowedAppIDs. If Apple Mail has to keep working for now, add the Apple ID to the list along with the existing IDs.
4. Ask the vendors of your backup, scanning and integration software about their Graph version and timing.
5. Roll out the new Outlook for Mac, for example through Intune or your MDM, and let people get used to it.
6. Put a reminder in the calendar for mid-March 2027. If the Apple update still isn’t out by then, move everyone to Outlook before 1 April.
7. After 1 April 2027, take the Apple ID off the list and switch EWS off.

For home users and small businesses

1. Check System Settings > Internet Accounts for an Exchange account from work or your own business.
2. Compare your inbox on the Mac and the iPhone. If the Mac is missing mail, this is probably the reason.
3. Install the new Outlook for Mac and sign in with the same account. Turn the account off in Mail if you don’t want double notifications.
4. If you have your own Microsoft 365 environment for your business, you are the admin. Ask your IT partner or whoever you buy Microsoft 365 from to check the EWS settings.
5. If you use Fantastical, click Migrate to Microsoft Graph in its account settings.
6. Update macOS as soon as Apple releases the Graph update, then check whether Mail syncs properly again.

Need help for your organisation? Email frank@analystict.nl.

This whitepaper describes the situation on 13 October 2026. Microsoft adjusts the rollout details regularly and Apple hasn’t given a date for the Graph update yet. Check the Microsoft 365 Message Center and the macOS release notes for the latest.

This article is part of the Mac and the rest of the world series, where you’ll find every part in one place.