Using the RelayCountry plugin
The RelayCountry plugin exposes the countries that a mail was relayed from – turn it on by reading that documentation page, installing the required CPAN module (see below), and uncommenting the 'loadplugin' line in the /etc/mail/spamassassin/init.pre file for Mail::SpamAssassin::Plugin::RelayCountry.
Required CPAN module dependencies, choose one:
GeoIP2::Reader::Database | Supported since SpamAssassin 3.4.2, install MaxMind::DB::Reader::XS for best performance |
IP::Country::DB_File | Supported since SpamAssassin 3.4.2 |
Geo::IP | Supported since SpamAssassin 3.4.0 |
IP::Country::Fast | Not recommended, outdated |
Country metadata will also be added to the Bayesian filtering process, allowing it to learn information based on countries.
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Perhaps the easiest to install, since most distributions package these.
Note that Geo::IP updates are discontinued since April 2018, so you should use the new GeoIP2 (MMDB) databases. Free and commercial versions can be found from several vendors:
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