Microsoft Is Switching Off a Bit of Plumbing Behind Your Email (Here's What Small Businesses Need to Know)

Note for readers: this mainly affects Mac users. If you and your team work on, Windows, iPhones, iPads, Android or with Outlook, you're not affected.

If you run your business email on Microsoft 365 or Microsoft Exchange, and you use the built-in apps on your Mac (Mail, Calendar, Contacts, Notes or Reminders), there's a deadline you need to know about: from 1 April 2027, Microsoft permanently switches off the old system those apps use to talk to your account.

Sounds dramatic. It's manageable. Here's the plain-English version.

First, the headline

Microsoft is retiring something called Exchange Web Services, or EWS. It's the behind-the-scenes protocol that lets Apple's Mac apps sync your work email, calendar and contacts with a Microsoft 365 account. It's been around since the late 2000s, and Microsoft is switching it off in stages. The final cut-off is 1 April 2027. After that, no app can use it, and Microsoft has said there will be no extensions.

Am I affected?

Here's the quick test:

• You use an iPhone or iPad with your Microsoft 365 or Exchange email? You're fine. Apple's mobile apps use a different connection method (ActiveSync) that Microsoft is keeping.

• You use Outlook (the app or the website) on any device? You're fine. Outlook already uses Microsoft's newer system.

• You use the Apple apps on a Mac (Mail, Calendar, Contacts, Notes or Reminders) for your Microsoft 365 or Exchange email? That's the group this affects. Once EWS is switched off, those apps stop syncing with your account. New emails won't arrive. Your calendar stops updating.

If that third bullet is you, keep reading. If not, you can carry on with your day 😊

What actually happens, and when?

Two dates matter:

1. 1 October 2026: Microsoft started phasing EWS out. Some businesses already noticed their Mac Mail or Calendar playing up around then.

2. 1 April 2027: EWS is switched off for good. Anything still relying on it stops working.

In between, whoever manages your email setup (you, if you're a sole trader, or your IT person) can temporarily switch EWS back on to buy time. But that door closes on 1 April 2027. This is not a "wait and see" situation, it's a diary date.

The good news: Apple is fixing this

Apple has confirmed it's updating Mail, Calendar, Contacts, Notes and Reminders on the Mac to use Microsoft's newer system (the Graph API) in a future update to macOS 27. So the built-in apps will very likely keep working in the long run, as long as you keep your Mac updated.

The catch: at the time of writing, that update hasn't landed yet. Nobody knows exactly when it will arrive, only that Microsoft's deadline won't move. So the sensible plan is to have a fallback ready, just in case.

What should you actually do?

If you're a solo operator:

1. Put a reminder in your calendar for early 2027 (say, January) to check whether Apple's update has arrived. If it has, install it and you're done.

2. Know your fallback: Outlook for Mac is included with a Microsoft 365 Business Standard subscription, and outlook.office.com works in any browser. Either one will happily run your email, calendar and contacts.

3. Keep your Mac updated so you get Apple's fix as soon as it ships.

Other points:

1. Check who's using the Mac Mail and Calendar apps with the company account. Anyone who is will be affected.

2. Consider moving them to Outlook for Mac or Outlook on the web now, on your own schedule, rather than scrambling in March 2027.

3. Watch out for anything else plugged into your email: booking tools, invoicing add-ons, CRM syncs and older scanner apps sometimes quietly use EWS too. If one of those stops syncing in early 2027, this retirement is the usual suspect.

The bottom line

• iPhone and iPad: nothing to do.

• Mac users of Apple's built-in apps: a fix is coming from Apple, but we don’t know when.

• Everyone else on Outlook: carry on.

If you take one thing from this: book ten minutes in January 2027 to check that Mail and Calendar on your Mac are still syncing. That's cheaper than discovering the problem when a client says your meeting invite vanished.

If you have any questions, or would like some help, please do reach out.