B2B Direct Connect and File Sharing Support

B2B Direct Connect alone does not replace Microsoft Teams external access configuration. Your requirements can largely be met while keeping users as native accounts in their respective tenants, but chat and file-sharing capabilities depend on the specific Teams collaboration model.

Native accounts, no Guests: You can retain each user's existing home-tenant identity. B2B Direct Connect does not require creating guest accounts for supported scenarios.

Trusted domain recognition: Teams external access domain restrictions are managed separately from Microsoft Entra cross-tenant access settings. Configure the three organizations' domains in the Teams Admin Center allowlist if required by your external access policy.

One-to-one chats: Configure Teams external access and Microsoft Entra cross-tenant settings as appropriate for your intended collaboration model. A B2B Direct Connect relationship alone does not automatically make a domain trusted by Teams.

File sharing and drag-and-drop: Do not assume B2B Direct Connect enables file attachments in every Teams chat scenario. File-sharing support depends on the collaboration type and the applicable Teams and SharePoint/OneDrive policies.

Recommended configuration

Microsoft Entra ID: Configure mutual inbound and outbound B2B Direct Connect access between all three tenants.

Teams Admin Center: Configure external access for the three domains to enable one-to-one chats. The allowlist is managed independently of B2B Direct Connect.

File sharing: Use Teams shared channels with B2B Direct Connect for guest-free collaboration, including channel chat and file sharing. Shared-channel files use SharePoint policies.

SharePoint/OneDrive: Verify the relevant sharing permissions and organizational restrictions.

Important limitation: B2B Direct Connect is currently designed for Teams shared channels; it does not by itself enable guest-free file attachments in standard one-to-one external chats. For one-to-one chat attachments, verify the supported collaboration model before changing policies.