The fortimail scanner can be configured to apply rules on individual users and any other mail for that domain which does not have a user setup. 

To add a new user you will need to login as the site administrator, click on Policy and then Recipient Based, 

 Under this menu click on Create New

This will then refresh the screen and allow you to enter a new user and select the anti spam, anti virus and content profiles to use for that user. 

The user is added to the system once you click ok.

You can see from the listing above there are three users, the testing and tester refer to users setup.  Whereas the asterisk refers to any other mail passing through the system for that domain.  You can move the user amongst the list so as to set priority of scanning, the rules are arranged down the list and so the asterisk is usually at the end.

To move the user through the list click on the image, , this will then ask to which position within the list to move the user to.

The new order is saved through the OK button