Cpanel provides Email filters to define different criteria, based on which emails arriving on to the domain/mail account is handled. There are two options available, the Global Email Filters and the Email filters at user level.
The global email filter does use the same set of criteria as in user level filtering with the exception that the rules set on global email filters are applicable to the whole domain. You can find the detailed set of options at Cpanel Documentation site
To create user-level or specific email account level filter:
1. Login to cPanel.
2. Click "Email Filter" in the Email section.
3. Select the email account and click "Manage Filters".
4. Then click the "Create a New Filter button".
5. Enter a name for the filter in the Filter Name text box.
6. Configure your filter's rules and actions.
7. Once it is done, click "Create" button.
Email filters also helps you define specific words or subject lines that should be removed or moved away from inbox. This helps in spam filtering. The criteria also includes spam score based filtering which also helps.
TESTING AN EMAIL FILTER
After you have created a filter, you should test it to make sure that it filters what you intended.
To test an email filter, follow these steps:
In the Email section of the cPanel home screen, click Email Filters or Global Email Filters.
If you are configuring a user-level filter, locate the account that has the filter you want to test, and then click Manage Filters.
In the Filter Test text box, type a test email message.
Click Test Filter. The Filter Trace Results page shows if any rule conditions were met, and whether or not any actions will be taken.
Thats All!