Microsoft 365 features that help users manage their subscriptions, account settings, and billing information.
Dear nabtech (nabtech),
Good day!
Thank you for posting to Microsoft Community. We are glad to assist.
As per your mentioned description about "how to block domains". Kindly check with below step to block email from a specific domain.
- Kindly go to Microsoft 365 admin center (Enter your username and Password)-->Show all-->choose Security under Admin centers or go to Microsoft 365 defender direct by visiting https://security.microsoft.com/
- Go to Policies & rules > Threat Policies > Rules section > Tenant Allow/Block Lists
- On the Domains & addresses tab, click
Block. - In the Block domains & addresses flyout that appears, configure the following settings:
- Domains & addresses: Enter the specific domain you want to block.
- Remove block entry after: The default value is 30 days, but you can select from the following values:
- 1 day
- 7 days
- 30 days
- Never expire
- Specific date: The maximum value is 90 days from today.
- Optional note: Enter descriptive text for why you're blocking the email addresses or domains.
- When you're finished, click Add.
Important Note:
- If you are not Admin, kindly contact your organization Admin to perform above steps.
- Users in the organization can't send email to these blocked domains and addresses. They'll receive the following non-delivery report (also known as an NDR or bounce message): 550 5.7.703 Your message can't be delivered because one or more recipients are blocked by your organization's tenant recipient block policy. The entire message is blocked for all recipients of the message, even if only one recipient email address or domain is defined in a block entry. For extra reference kindly refer to Allow or block email using the Tenant Allow/Block List - Office 365 | Microsoft Learn
Please feel free to let me know if there are any updates or if I've got you wrong. I will keep assisting you based on the information you provide. We sincerely appreciate your patience and cooperation. Thanks for your precious time. Have a nice day!
Best regards,
Inema | Microsoft Community Moderator