Mail Stopped Syncing in October? Microsoft Turned Off EWS

If your work email stopped syncing in Apple Mail on your Mac, or a tool connected to Microsoft 365 stopped working in October, the cause is almost certainly that Microsoft has started switching off Exchange Web Services (EWS). Your admin can switch it back on for the apps you need, today. That fix only lasts until 1 April 2027, so the real fix is moving off EWS before then.

Below is the whole fix, step by step, including the exact settings for whoever manages your Microsoft 365. If you’d rather not do it yourself, we can help. The first check is free.

What happened

EWS is an old way for apps to connect to your Microsoft 365 mailbox: read email, sync the calendar, look up contacts. Microsoft is retiring it from Exchange Online, the email behind Microsoft 365.

1 October 2026: Microsoft started switching EWS off, organisation by organisation, unless an admin had set it up to stay on.
1 April 2027: EWS is removed completely, with no option to switch it back on.

Company email servers that businesses run themselves (“on-premises” Exchange) are not affected. This is only Microsoft 365.

Who is affected

Apple Mail and Calendar on a Mac. This is the big one. Apple’s own documentation says Mail and Calendar on macOS use EWS for Microsoft 365 accounts. Apple says it is working with Microsoft to move them to the new connection “in a future update to macOS 27”, but there’s no date yet. iPhone and iPad are not affected. They use a different connection.

Tools that plug into your mailbox or calendar, for example:

Older CRM and sales tools that log your emails
Booking and scheduling tools that check your Outlook calendar
Email archiving and backup tools
Some scanner and printer workflows that deliver to a mailbox
Custom scripts or small apps someone built for you years ago

Usually not affected: the current Outlook apps on Windows and Mac, Outlook on the web, and phones.

Quick check: is it EWS?

Does your email still work at outlook.office.com, or on your phone, but not in Mac Mail or the tool? Then the account is fine and the connection is the problem. That’s EWS.
Did it stop around early October, with nothing changed on your side? That’s EWS.
Still not sure? Whoever manages your Microsoft 365 can open the EWS usage report (below). It lists every app still using EWS.

What waiting costs

This rarely announces itself. Mail quietly stops arriving on the Mac, calendar bookings stop syncing, emails stop being saved to the CRM. Meanwhile customers wait for replies, the same slot gets booked twice, and leads go unanswered. Every week it stays broken is a week of that.

Fix it today

If you’re on a Mac with no IT person

Use Outlook for Mac in the meantime. It’s free with Microsoft 365, uses the newer connection and keeps working. You can also use Outlook on the web at outlook.office.com.
Or ask whoever set up your company email to do the admin steps below so Apple Mail works again until April.
Don’t delete and re-add your account in Apple Mail. If EWS is the problem, that won’t fix it, and you may lose local settings.

For whoever manages your Microsoft 365 (the admin steps)

These are Microsoft’s documented options for keeping EWS working for specific apps until April 2027.

1. Find out which apps use EWS. In the Microsoft 365 admin center go to Reports → Usage → Exchange Online → EWS usage. It lists the app IDs calling EWS and how much they use it. Export it.

2. Connect to Exchange Online PowerShell and check the current setting:

Connect-ExchangeOnline
Get-OrganizationConfig | Select-Object EwsEnabled

3. Switch EWS on, but only for the apps you need, using their app IDs from the report:

Set-OrganizationConfig -EwsEnabled $true -EwsAllowedAppIDs "first-app-id,second-app-id"

4. Check the list took:

Get-OrganizationConfig -RetrieveEwsOperationAccessPolicy | Format-List EwsAllowedAppIDs

Three things that catch people out

There’s no “add” option. Each time you change the list you must pass the complete list, or you’ll remove apps that were on it.

An empty list blocks everything, even with EWS switched on.

Changes can take up to 24 hours to apply. Don’t assume it failed after five minutes. The list Microsoft builds automatically is based on about 60 days of usage, so a tool that only runs now and then can be missed.

Fix it properly before April

The steps above buy time. On 1 April 2027 they stop working for everyone. Before then, each app has to move to Microsoft Graph, the connection Microsoft replaced EWS with:

Apple Mail: wait for Apple’s macOS update. If it hasn’t arrived by early 2027, move Mac users to Outlook for Mac before 1 April.
Bought tools (a CRM, booking or backup product): ask the vendor one question: “Does your product use Microsoft Graph instead of EWS, and if not, when?” A good vendor has a date. One without an answer is telling you to look for a replacement.
Custom scripts and in-house apps: these need rewriting to use Graph. Microsoft publishes a map of which EWS features have Graph equivalents. Most common jobs (reading mail, calendars, contacts) are covered. A few, like some archive and public folder operations, are still catching up, so check before you start.
Something you barely use: retire it rather than fix it.

April 1 is under six months away, and every developer who does this work will be busy in March. If you have a custom tool, start now.

How to not be here again

The pattern is always the same: something you rely on is connected to something else through a link you didn’t choose and can’t see. Then a vendor changes it.

The habit that prevents it is boring and works: keep a short list of every tool that touches your email, calendar, website and payments, who supports it, and how it connects. When a notice like Microsoft’s lands, you check the list in five minutes instead of finding out from a customer.

Related reading: You’re being moved to an AI plan you didn’t ask for covers the same pattern with AI pricing. What to do when your web host goes down is the hosting version of a tool disappearing overnight. And n8n vs Zapier vs Make helps if you’re rebuilding a broken connection and want to choose the tool properly this time.

Sources: Microsoft Learn: Deprecation of EWS in Exchange Online · Microsoft message center MC1227454 · Apple Platform Deployment: Integrate with Microsoft Exchange · MacRumors, October 2026 · PowerShell steps as documented by LazyAdmin, checked against Microsoft’s guidance. Last checked 15 October 2026.