To block mail from specific domains, create a policy in IMSVA and use the Header keyword expressions as a condition to match the domain.

1. Log in to IMSVA web console.
2. Go to Policy > Policy List.
3. Create a new policy by clicking Add and then select Others.
4. Under Step 1: Select Recipients and Senders, assign the values for the following:
   • Recipients - <your company's email domain>

     For example: test@mycompany.com

   • Senders - *@*.domain.com

     Ex: *@*.domain.com

5. Click Next.
6. Under Scanning Conditions, go to the Content section, tick the Header keyword expressions option and click it to configure its setting.
7. Under Specific headers match, tick the From checkbox.
8. Click Add to create a Keyword Expression.
9. On the Match field, select Any specified.
10. Click Add and type following keyword expression values:

    \w+([\.-]?\w+)*@[\s\S]+\.domain\.com (This can match xxx@xxx.domain.com.)
    \w+([\.-]?\w+)*@domain\.com (This can match xxxx@domain.com.)

11. Click Save
12. Save and then select the Header keyword expression. Then click Next.
13. Select the action for the rules that you created. For example, Quarantine, Delete entire message, etc.
14. Assign a Policy Name and Order Number for your policy. The Order Number indicates the priority of the rule, with 1 being the highest priority.
15. Save the new policy.