You try to use Copilot in Microsoft Teams to summarize a chat that includes participants from outside your organization, but Copilot returns an error or a blank response. This failure occurs because Copilot relies on Microsoft Graph data access policies that restrict processing of content from external tenants for security and compliance reasons. This article explains the root cause, provides step-by-step fixes to enable cross-tenant chat summarization, and covers related failure patterns.
Key Takeaways: Fixing Copilot Summarization for External Chats
- Microsoft 365 admin center > Settings > Org settings > Copilot > Cross-tenant data access: Enables Copilot to read messages from external chat participants when summarization is requested.
- Teams admin center > Messaging policies > Copilot for Teams: Must be set to On for the user group that includes external chat participants.
- Azure AD cross-tenant access settings > Inbound access > Trust settings: Required to allow external user claims to be processed for Copilot summarization.
Why Copilot Cannot Summarize External Chat Conversations
Copilot in Teams uses Microsoft Graph to access chat history, participant profiles, and message content. When a chat contains participants from an external Microsoft 365 tenant, Graph blocks Copilot from reading that participant’s messages unless cross-tenant data access is explicitly allowed. This restriction is enforced by default to prevent data leakage between organizations.
The root cause is a missing or misconfigured cross-tenant access policy in Azure Active Directory and a corresponding Copilot data access setting in the Microsoft 365 admin center. Without these policies, Copilot treats the entire chat as partially restricted and refuses to generate a summary. The error message typically reads: “Copilot cannot summarize this conversation because it contains participants from outside your organization.”
Steps to Enable Copilot Summarization for External Chats
You must configure three settings in sequence. Perform these steps as a Global Administrator or Teams Administrator.
1. Configure Cross-Tenant Data Access in Microsoft 365 Admin Center
- Open the Microsoft 365 admin center
Sign in at admin.microsoft.com with an account that has Global Admin or Copilot Admin role. - Navigate to Copilot settings
Go to Settings > Org settings > Copilot. - Enable cross-tenant data access
Select the tab labeled Cross-tenant data access. Toggle the setting Allow Copilot to access data from external Microsoft 365 tenants to On. Click Save. - Add the external tenant domain
In the same section, click Add tenant. Enter the domain name of the external organization whose chat participants you want Copilot to summarize. For example, contoso.com. Click Add and then Save.
2. Configure Azure AD Cross-Tenant Access Settings
- Open Azure Active Directory
Go to entra.microsoft.com and sign in as a Global Administrator. - Access cross-tenant settings
Navigate to Identity > External Identities > Cross-tenant access settings. - Configure inbound trust for the external tenant
Under Organizational settings, locate the external tenant. Click the Inbound access tab. Under Trust settings, check the box Trust claims from this tenant. This allows Copilot to process user claims from that tenant. Click Save. - Configure outbound trust
Switch to the Outbound access tab. Under Trust settings, check Trust claims from my tenant. This ensures the external tenant can send user context back to Copilot. Click Save.
3. Verify Teams Messaging Policy for Copilot
- Open Teams admin center
Go to admin.teams.microsoft.com. - Check messaging policies
Navigate to Messaging policies. Select the policy assigned to the users who need to summarize external chats. The default policy is Global (Org-wide default). - Enable Copilot for Teams
Find the setting Copilot for Teams. Set it to On. Click Save.
If Copilot Still Has Issues After the Main Fix
Copilot Returns an Error About Data Residency
If the external tenant stores data in a different geographic region, Copilot may still refuse to summarize. To fix this, both tenants must have multi-geo capabilities enabled. Contact Microsoft Support to enable multi-geo for your tenant. After multi-geo is active, re-run the cross-tenant data access configuration from step 1.
Copilot Shows Partial Summaries Missing External Messages
This occurs when the cross-tenant trust settings are correctly configured but the external tenant has not enabled the same settings on their side. Ask the external organization’s administrator to repeat steps 1 and 2 in their own tenant. Both sides must allow cross-tenant data access for Copilot to read all messages.
Copilot Does Not Appear in the Chat Window at All
Check that the user has a Copilot for Microsoft 365 license assigned. Go to Microsoft 365 admin center > Users > Active users, select the user, and verify the license includes Copilot for Microsoft 365. If the license is missing, assign it and wait 15 minutes for propagation.
Copilot Summarization: Internal vs External Chat
| Item | Internal Chat | External Chat |
|---|---|---|
| Default Copilot behavior | Summarizes all messages | Returns error or blank |
| Graph data access required | Automatic | Requires cross-tenant policy |
| Azure AD trust settings needed | None | Inbound and outbound trust |
| Teams messaging policy | Copilot for Teams must be On | Copilot for Teams must be On |
| Data residency impact | None | May require multi-geo |
Conclusion
You can now configure cross-tenant data access in the Microsoft 365 admin center, set Azure AD trust settings, and enable the Teams messaging policy to allow Copilot to summarize external chat conversations. Verify each setting in order: admin center cross-tenant toggle, Azure AD inbound and outbound trust, and Teams Copilot policy. As a next step, test summarization with a chat containing one external participant. For persistent issues, ask the external tenant to mirror the cross-tenant data access settings on their side.