Can you block incoming communication to a domain without blocking outgoing to that domain?

Hi @Pablo Fernandez,

Good day! Thank you for reaching out to Microsoft Q&A forum and sharing the detail.

Regarding your concerns, currently Teams does not support one-way federation at the domain level. External access settings are symmetric, if a domain is allowed, both sides can initiate communication; if blocked, both directions are blocked. Microsoft Teams’ external access policies are designed for mutual communication between organizations. There is no built-in option to allow outbound messages while preventing inbound messages from the same domain. 

You can consider the following two workarounds: 

1. Closed Federation and Targeted User Policy
   • Configure Teams to allow only the client’s domain and assign external access permissions only to specific users or groups (such as your customer-facing team), but these users can still receive inbound messages from the client; it’s not a true one-way setup. 
   • Kindly refer the document: Manage external meetings and chat with people and organizations 
2. External User Block List

• Block specific external accounts from contacting your users while keeping the domain allowed. However, this works only for individual accounts, not the entire domain, and requires ongoing maintenance if new users are added on the client side. 
  • Kindly refer the document: Block domains in Microsoft Teams using the Tenant Allow/Block List 

In your case, I highly suggest raising a support ticket through the Microsoft 365 Admin Center (kindly request your admin if you're not). Microsoft’s senior Teams support engineers have deep expertise and can provide the most accurate guidance and, in some cases, offer tenant-specific configurations or roadmap insights. For detailed instructions on how to get support, please refer to Get support - Microsoft 365 admin.

I appreciate your understanding, should you have any further questions please free to reach out.

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