Microsoft Is Switching Off EWS in Exchange Online: What UK Businesses Should Check

Microsoft began disabling Exchange Web Services (EWS) across Exchange Online in October 2026, and says EWS will be fully disabled in April 2027. UK businesses on Microsoft 365 should check which apps still use EWS, such as older CRMs, backup tools, scanners and some Mac mail setups, and ask suppliers how they are moving to Microsoft Graph.

If someone in your business has suddenly lost calendar sync, or an integration that files emails has stopped, this change is a likely suspect.

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What happened

EWS is an old interface that lets software read and send mail, calendar entries and contacts in Exchange. Microsoft stopped adding features to it in 2018 and set October 2026 as the disablement date in 2023.

Microsoft's EWS deprecation page on Microsoft Learn gives the timeline:

Microsoft says the Midnight Blizzard incident in January 2024 "involved EWS and elevated the urgency of the EWS deprecation effort". The details of the phased process are in the Exchange Team's post Exchange Online EWS, Your Time is Almost Up, and Microsoft has published a separate post for admins whose EWS applications have stopped working.

What about Apple Mail?

AppleWorld Today reported on 1 October 2026, crediting MacRumors, that Apple's Mail and Calendar apps on Mac still rely on EWS to sync Microsoft 365 work accounts, and that organisations which kept EWS enabled are not affected for now. Microsoft's deprecation page does not mention Apple's apps, so treat this as a credible report rather than a confirmed list. If your team uses Mail on Mac with Microsoft 365, test it now and have a fallback ready, such as Outlook for Mac.

Who this affects in the UK

• Small businesses on Microsoft 365 with any third-party tool connected to mailboxes: CRMs, practice management systems, email archiving, backup, signature tools or scan-to-email devices.
• Mac users syncing work email or calendars through Apple's built-in apps.
• IT providers and MSPs managing many tenants, who will field the support calls.
• Accountancy, legal and recruitment firms, which may rely on older integrations that file emails against client or candidate records.

Microsoft also says it is removing EWS dependencies from its own products, including Outlook, Office, Teams and Dynamics 365, and some Excel and Power BI connectors are changing.

Practical checklist

1. Open the EWS usage report. In the Microsoft 365 admin centre, Microsoft provides EWS Usage Reports showing which apps use EWS.
2. List every connected app and the person who owns it in your business.
3. Contact each vendor. Ask whether their product has moved to Microsoft Graph and what you need to change. Get the answer in writing.
4. Test Mac Mail and Calendar if staff use them for work accounts. Move them to Outlook for Mac if sync fails.
5. Check scanners and multifunction printers that send email, and any old scripts or automations your IT provider built.
6. Use the temporary admin controls carefully. Microsoft's guidance explains how admins can manage EWS during the phased rollout, but April 2027 is the end point, so treat any re-enablement as buying time, not a fix.
7. Review admin security. Make sure every Microsoft 365 admin account uses multi-factor authentication; our guide to two-factor authentication covers why.
8. Recheck your email authentication while you are in the admin centre. Run your domain through our free SPF checker, DKIM checker and DMARC checker, and confirm your MX records are correct.

For a wider review of client tenants, see our MSP email security audit. Firms with sensitive client data may also find our guides on email security for solicitors and email fraud protection for accountants useful. Make It Flow's free tools for IT services and accountants help with the checks.

FAQ

What is Exchange Web Services (EWS)?

EWS is an older programming interface that lets apps access Exchange mailboxes, calendars and contacts. Microsoft stopped adding features in 2018 and is replacing it with Microsoft Graph. In Exchange Online, Microsoft began disabling EWS globally in October 2026 and plans to disable it fully in April 2027.

Will Outlook stop working?

Microsoft says it is removing EWS dependencies from its own products, including Outlook, Office, Teams and Dynamics 365. The main risk is third-party apps and integrations that still rely on EWS. Keep Outlook updated and check the EWS usage report for other apps.

Does this affect Apple Mail on Mac?

Apple-focused news sites reported on 1 October 2026 that Mail and Calendar on Mac rely on EWS for Microsoft 365 work accounts. Microsoft's own deprecation page does not name Apple's apps. If your staff use them, test sync now and have Outlook for Mac ready as a fallback.

Can my IT provider turn EWS back on?

Microsoft has published guidance for admins whose EWS applications have stopped working during the phased rollout. Any re-enablement is temporary, because Microsoft says EWS will be fully disabled in April 2027. Use the time to move affected apps to Microsoft Graph or replace them.

Does this affect on-premises Exchange Server?

Microsoft's deprecation page covers Exchange Online, the cloud service in Microsoft 365. If you run your own Exchange Server, check Microsoft's separate guidance for on-premises Exchange and speak to your IT provider, as this timeline does not describe it.

Sources

• Microsoft Learn: Deprecation of Exchange Web Services in Exchange Online
• Microsoft Tech Community: Exchange Online EWS, Your Time is Almost Up
• Microsoft Tech Community: Exchange Online EWS application stopped working? Do this
• Microsoft Learn: EWS usage reports
• AppleWorld Today: Microsoft is now disabling EWS by default in Exchange Online (1 October 2026)