Using the RelayCountry plugin

The [http://spamassassin.apache.org/full/3.0.x/dist/doc/Mail_SpamAssassin_Plugin_RelayCountry.html RelayCountry] plugin exposes the countries that a mail was relayed from – turn it on by reading that documentation page, installing the CPAN module required {cpan IP::Country::Fast, and uncommenting the 'loadplugin' line in the /etc/mail/spamassassin/init.pre file for Mail::SpamAssassin::Plugin::RelayCountry.

Once this plugin is running, you can write rules that match specific countries, e.g.:

   header CAME_VIA_CHINA   X-Relay-Countries =~ /CN/