To ban email and IP addresses go to CRM > User Banning to stop them from being used to submit Tickets or register accounts.

To ban an email, you can either ban a single email address or an entire domain. You would have to select the Banned Emails tab and then select + New. You can then list the Email Address Pattern and select Create at the bottom of the panel.

The same goes for banning IP addresses, you would have to select the Banned IPs tab and then select + New. You can then list the IP Address Range and then select Create at the bottom of the panel.