Adding an email address to a block list means you will never accept message from that sender into your inbox, automatically filtering them out as unwanted mail.
You can set email addresses to your block list through your hosting control panel. Please note that when you add an email address to a block list, this action is specific to each individual domain and email address.
1. Log in to your hosting control panel
2. From the top right, next to the Domain: field, click on your domain name and select the domain name you want to manage
3. Click on the Spam Management button
4. Locate the Blacklisted E-mails section
5. In the provided field, type in the email address you want to add to your block list and click the enter key on your keyboard to save it