Emails from a company (domain), sender, or IP, can be added to an allow or block list at the corporate level or at the user level.
Here's how to allow or block people, company or mailing lists from sending you emails at the corporate level:
Log into the Software/Appliance as the Administrator and navigate to Anti-Spam | Address Books.
Select the Blocked button.
Here is where the blocked senders email address, domain, or IP, are listed and can be added. The process for the user level list is the same except instead of logging in as admin, the user would need to login to their junk box.
The Administrator can also perform this action by going to Users, Groups & Organizations | Users then select the user and click on sign in as user. When a company, sender, or IP, is added to a blocked list, future messages from that sender/company/IP will be considered spam and will be stored in the junk box.