Microsoft explains how to fix broken Exchange Online EWS apps

Microsoft began blocking the retired Exchange Web Services API in Exchange Online by default on October 1, 2026. Admins can temporarily re-enable EWS via Baseline Security Mode or the Set-OrganizationConfig -EWSEnabled $true command, but this option ends in April 2027.

• EWS is blocked by default from October 1, 2026, with final shutdown on April 1, 2027
• Admins can re-enable EWS by unchecking the block in Microsoft 365 admin center
• The Set-OrganizationConfig -EWSEnabled $true command takes effect within 4 hours
• Developers are advised to migrate to the Microsoft Graph API before shutdown