An email filter is used to perform a specific action, for example eliminate all messages with a certain subject or redirect them somewhere else.
Login to cPanel and click on "Email Filters" in the EMAIL section.
You will see a list of your email accounts and a link to manage filters.
After clicking on manage filters you can see the filter's list (if you already have some). In this example there are no filters since this is the first one that we are creating. You can click on the button to create a new filter.
You will see a screen that allows you to add a filter. Add a name for your filter to remember what it does, then set the rules and the actions you want to perform. Clicking on the buttons on the right you can add more rules and more actions for your filter.