Yes you can list an entire country code or any other top level domain or subdomain using the Black/White List (Filters > Black/White List).

To block a whole domain or subdomain, simply add that domain to the black list:

1. Log into your PerfectMail web interface using an administrator account;
2. Navigate to the Black/White List page (Filtering >Black White List) and select the Black List tab;
3. Add the Top Level Domain Country Code to the Black List. For example, to block the Soviet Union you would add an entry for "SU" to the list (not ".su" nor "*.su"; simply use "su"). Any e-mail coming from any domain ending ".su" or from any hostname ending ".su" will be black listed.

Internet domain country codes are listed by IANA in ISO 3166-1.

You can find a list of country codes at this link: http://perfectmail.com/kb/100088