If someone on your team uses a Mac and their work email, calendar or contacts suddenly stopped updating this month, or Apple Mail keeps asking for their password, the problem probably isn't their Mac. Microsoft is switching off an old connection called Exchange Web Services (EWS) in Microsoft 365, and a surprising number of apps still depend on it.
What's changing
EWS is the older way that apps connect to email, calendars and contacts in Microsoft 365. Microsoft has replaced it with a newer, more secure connection (Microsoft Graph), and is now retiring EWS in two steps:
- —From 1 October 2026, Microsoft is turning EWS off business by business. If your Microsoft 365 admin didn't set it up to stay on (Microsoft's deadline for that was the end of August), it gets blocked automatically.
- —On 1 April 2027, EWS switches off for everyone, permanently. Microsoft has said there will be no extensions.
This only affects Microsoft 365 (Exchange Online). Businesses that run their own Exchange server aren't affected.
What stops working
- —Apple Mail, Calendar and Contacts on a Mac, when your work account was added as an Exchange account. Typical signs: email stops arriving, the calendar stops updating, or Mail asks for your password again and again.
- —Old Outlook for Mac (the legacy version). It stops working with Microsoft 365.
- —Some third-party tools that read your mailboxes or calendars: older email backup tools, CRM email and calendar sync, booking and scheduling tools, email signature tools and migration tools. They often fail quietly, so nobody notices until something is missing.
- —Custom scripts or in-house apps someone built years ago to read mailboxes.
What keeps working
The good news: most people won't notice anything. Outlook for Windows, the new Outlook for Mac, Outlook on the web, the Outlook mobile app, and the built-in Mail app on iPhone and iPad all keep working as normal.
The fix for Mac users
If someone on your team uses Apple Mail or old Outlook for Mac for work email, move them to the new Outlook for Mac. It's included with Microsoft 365 business plans and uses the new connection, so it won't be affected.
- —Download Microsoft Outlook from the Mac App Store (or open Outlook and switch on New Outlook if they already have it).
- —Sign in with their work email address. Email, calendar and contacts come straight through.
- —Remove the old Exchange account from Apple Mail (Mail → Settings → Accounts) so they don't get confusing errors or duplicate reminders.
- —In the meantime, anyone can read their email at outlook.office.com in a browser, so nobody is cut off while you sort it out.
Personal email accounts in Apple Mail (like iCloud or Gmail) aren't affected. This is only about Microsoft 365 work accounts.
The fix for apps and tools
Tools are harder to spot, because they don't show an error to anyone. Work through this list with whoever manages your Microsoft 365:
- —List the tools that touch your email or calendars: backup, CRM, booking, email signatures, archiving, and anything that syncs contacts.
- —Check Microsoft's EWS usage report in the Microsoft 365 admin centre (under Reports). It shows which apps still connect using EWS.
- —Ask each vendor: “Do you use Microsoft Graph or EWS? If EWS, when are you switching?” Most well-known tools have already updated. Older or smaller ones may need an update, a new connection, or replacing.
- —Check your backups actually ran. Look at the latest backup report for your mailboxes, rather than assuming it's fine. A backup that quietly failed in October is the one you'll miss most.
- —If a tool can't be updated in time, your admin can ask Microsoft's support about allowing just that app temporarily. It will only buy time until 1 April 2027, so plan the replacement now.
Your quick checklist
- —Ask your team: who uses a Mac for work email, and which app?
- —Move Apple Mail and old Outlook for Mac users to the new Outlook for Mac.
- —Check the EWS usage report in the Microsoft 365 admin centre.
- —Confirm with each backup, CRM, booking and signature vendor that they've moved off EWS.
- —Check your latest mailbox backup actually completed.
- —Put 1 April 2027 in the diary as the final deadline.
Part of a bigger clear-out
EWS is one of several older Microsoft technologies retired this year, along with SharePoint Alerts, Microsoft Publisher and the one-time codes clients used to open shared links. If one of these caught you out, it's worth checking the rest. My free Microsoft 365 setup checklist covers the basics.
If you'd rather have someone check it for you, my Microsoft 365 setup service includes reviewing the apps connected to your Microsoft 365 and moving your team onto supported tools.
