Exchange Online blocks EWS access by default from 1 October, leaving some apps unable to connect

According to an IT-Connect report dated 23 October 2026, Microsoft began blocking Exchange Web Services (EWS) access in Exchange Online by default from 1 October 2026. Tenants that had not set up an allow list in advance have their EWSEnabled setting switched to False; because the switch is being phased in around the world, some tenants may not see it yet. Microsoft announced this timeline on the Exchange team blog in February 2026.

• IT-Connect lists EWS-dependent software such as Outlook add-ins, Apple Mail and Calendar on macOS, older Outlook for Windows releases and third-party tools as affected; symptoms include business apps that cannot connect and repeated password prompts.
• Admins can turn access back on from Baseline security mode in the Microsoft 365 admin center or with Exchange Online PowerShell; the change can take up to 4 hours to apply.
• Microsoft builds a list of apps based on usage detected over the last 60 days; app IDs added to the allow list can take up to 24 hours to take effect.
• According to the Exchange team, EWS will be fully shut down in the cloud on 1 April 2027 and admins will no longer be able to change the setting; on-premises Exchange Server is not affected.

Why it matters

If a company in Türkiye runs software that uses EWS for e-mail archiving, backup, CRM and ERP integration or calendar sync, that application can lose its connection. Turning access back on only buys time until April 2027. Moving applications to Microsoft Graph is recommended as the permanent fix. IT teams may find it useful to review the EWS usage report in the admin center, list the affected applications and ask their vendors for a Graph migration schedule.

We explain how connections between e-mail and business applications are built on our integration page.