How to Enable Shared Channels with External Organizations

While sharing shared channels externally is enabled by default in Teams, Azure Active Directory cross-tenant access settings for B2B direct connect must also be configured to share a channel externally. By default, these settings are set to block all organizations.

You can change the B2B direct connect default settings to allow all organizations. This allows users to collaborate in shared channels without your organization having to create a separate configuration for each organization that you want to collaborate with. (Note that the organizations you collaborate with will also have to configure their B2B direct connect settings.)

If your organization doesn’t have a requirement to restrict collaboration with other organizations, enabling all organizations by default can save you time and complexity in managing each organization separately.

 Note

Changes to cross-tenant access settings may take two hours to take effect.

Allow users to invite people in other organizations to participate in shared channels

You can allow your users to invite people from other organizations to use shared resources – such as shared channels in Teams – by default.

To allow users to invite B2B direct connect participants by default

1. Sign in to Azure Active Directory using a Global administrator or Security administrator account.
2. Select External Identities, and then select Cross-tenant access settings (preview).
3. On the Default settings tab, under Inbound access settings, select Edit inbound defaults.
4. Select the B2B direct connect tab.
5. On the Users and groups tab, under Access status, choose Allow access.
6. On the External applications tab, under Access status, choose Allow access.
7. Select Save.
8. Select the Trust settings tab.
9. Choose if you want to trust multi-factor authentication, compliant devices, or hybrid Azure AD joined devices from other organizations.
10. Select Save.
11. Close the Default settings blade.

Allow users to participate in shared channels in other organizations

You can allow your users to access resources that are hosted by an external organization – such as shared channels in Teams – by default.

To allow users to access resource from other organizations by default

1. In Azure Active Directory, select External Identities, and then select Cross-tenant access settings (preview).
2. On the Default settings tab, under Outbound access settings, select Edit outbound defaults.
3. Select the B2B direct connect tab.
4. On the Users and groups tab, under Access status, choose Allow access.
5. On the External applications tab, under Access status, choose Allow access.
6. Select Save.
7. Close the Default settings blade.

Ref: Enable shared channels with all external organizations | Microsoft Docs