Spam registrations on my Site

Hello Team,

I have been receiving too many notifications that users from A domain are registering to my site. That’s impossible and fake since it seems to be a Japanese Email page 163.com. I would like to know how can I block this specific domain to prevent registering to my site and if possible block the IP where this user is coming from.

Thanks in advance for the support!

The page I need help with: [log in to see the link]