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.

The [http://spamassassin.apache.org/full/3.0.x/dist/doc/Mail_SpamAssassin_Plugin_RelayCountry.html RelayCountry] plugin will add metadata to the Bayesian filtering process, allowing the Bayesian filters to learn information based on countries.

When using SA 3.1.0, you can also write rules that match specific countries, e.g.:

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