...
You can find this section
...
in HostBill Admin → Settings → Security Settings → Banned Emails.
...
This
...
feature allows you
...
prevent
...
registrations from
...
specific email domains.
To add email domain to banned list simply enter the domain, optionally add the ban reason and choose if/when the ban should expire.
Users that will try to register using email accounts from
...
listed domains will get error message about rejected email, with reason you provided when adding that restriction.
Each entry also
...
provides a counter that shows how many times this domain was rejected.