Update Exchange Web Services (EWS) allow list configuration for calendar

🚨 The Signal: Microsoft Teams mobile calendar will update backend services, requiring organizations using Exchange Web Services (EWS) application access policies to potentially update their allow lists to maintain functionality. Failure to update could disrupt Teams mobile calendar access.

The Impact

Exchange Online admins are affected; incorrect EWS configuration poses a service availability risk to Teams mobile calendar.

• Exchange Online Admins: Must review and update EWS allow lists.
• Teams Mobile Users: May experience calendar access disruption if EWS is not updated.
• Security Teams: Need to ensure EWS policies align with service continuity requirements.

The Action

1. Identify if your organization uses EWS application access policies (e.g., AllowList, EnforceBlockList).
2. Review existing EWS application access policies for allowed user agents.
3. Consult Microsoft documentation for the specific user agents or application IDs required for updated Teams calendar services.
4. Update EWS allow lists or block list exceptions to include the necessary Teams user agents via Exchange Online PowerShell.
5. Test Teams mobile calendar functionality post-update to confirm continuity.

Domain: Exchange · Impact: medium · Workload: Exchange Online