External access lets your teams communicate with other users outside of your organization.
IMP Note: This step must be completed on both tenants in order for them to communicate with one another.
Steps:
Login to Teams Admin Panel (admin.teams.microsoft.com) > Users > External access > ‘Choose which external domains your users have access to: > Allow only specific external domains.
Now Click on ‘Allow domains’ > Enter the domain name you want o allow > Done > Save.
Click on Confirm.
