To block emails from a specific email address, you must add an email filter in your cPanel.
To block a specific email from all of your email accounts
Under the section Email, click on Global Email Filters
Under Create Filter, click on Create a new filter
Enter the following information:
Filter Name: any name you wish to use
Under Rules: From - equals - EMAIL (EMAIL should be the address you wish to block)
Actions: Discard Message
Click on Create
To block a specific email from on only one of your email accounts
Under the section Email, click on Email Filters
Next to the email address you want to affect, click Manage Filters
Under Create Filter, click on Create a new filter
Enter the following information:
Filter name: any name you wish to use
Under Rules: From - equals - EMAIL (EMAIL should be the address you wish to block)
Actions: Discard Message
Click on Create