If an agent blocks a customer, then all the tickets created by that customer or by any agent on behalf of that customer are marked as SPAM.
Blocking a customer
Click on Customers.
Click on the customer name you want to block.
Click on the three-dot menu.
Click on Block.
A modal should be displayed.
Click on Block.
There is another way to block a customer. Whenever a ticket is marked as "spam," then a confirmation modal comes up asking if you also want to block the customer who created that ticket.