Microsoft 365 Defender
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      O365 Email Domain Block Work Instruction

      This work instruction will allow an administrator to specify a domain or address that users will no longer be able to communicate with.

      This article is intended for employees of organizations that use Sittadel's security. Additionally, there are some actions that can only be accomplished by those with administrative privileges.

      Procedure Scope: Administrators

      Required Group Membership: Admin.EmailSecurity

      1. Navigate to Tenant Allow/Block Lists – O365 Defender, select Block under the Domains/Addresses tab.
      2. In the following window you can specify either the entire domain or specific addresses associated with a domain (max limit of 20). Specify the timeframe as Never Expire and provide a reference point for fellow administration on why the block has been instated. Click Add.

      You're Finished!

      You should have successfully blocked the specified address or domain from having mail reach a user's inbox, this mail will instead show up in the administrative email quarantine queue. Additionally, user's will not be allowed to email the blocked address or domain. For any other problems or questions, reach out to us!