It's hard to stop e-mail SPAM completely but you can filter, discard or deliver it to selected folder etc.
How to create user level e-mail filter?
1. Log into your cPanel account.
2. In the "Email" section, click on the "Email Filters" icon.
3. Under "Filters by Users" you will see all your existing e-mail accounts. Click on the "Manage Filters" button next to the desired e-mail. 
4. Click on the "Create a New Filter" button.
5. Enter a name for the filter in the "Filter Name" field.
6. In the filter rules you can filter e-mails by many options and, for example, if you want to filter e-mails which contains a word "Lottery" or other words, then under the "Rules" select "Contains" and "Body" in the dropdown menu.
7. Under "Actions", select "Discard Message" in the dropdown menu.
8. Now click on the "Create" button.
This filter will discard all the e-mails for the selected user with the word "Lottery" in them.
