This article explains how you can adjust your SpamAssassin score using countries.nerd.dk DNSBL blocklist.
The zone contains information which can be used to determine whether a given IP address resides in a given country, thus making it possible for the users to filter out mail from a specific country using standard methods. For example my own mailserver is configured to reject mail from hosts listed in cn.countries.nerd.dk, which means that I should reject most mail sent from or through a mail-server located in China.
The zone contains no information about the status of an address as a spammer or open relay. In general terms: The zone does not contain anything but geographic information
describe BL_COUNTRY_VN_1 Mail client in Vietnam header BL_COUNTRY_VN_1 eval:check_rbl('vietnam', 'vn.countries.nerd.dk') score BL_COUNTRY_VN_1 2.0 # please adjust the score value tflags BL_COUNTRY_VN_1 net describe BL_COUNTRY_IN_1 Mail client in India header BL_COUNTRY_IN_1 eval:check_rbl('India', 'in.countries.nerd.dk') score BL_COUNTRY_IN_1 2.0 # please adjust the score value tflags BL_COUNTRY_IN_1 net describe BL_COUNTRY_RU_1 Mail client in Russia header BL_COUNTRY_RU_1 eval:check_rbl('Russia', 'ru.countries.nerd.dk') score BL_COUNTRY_RU_1 2.0 # please adjust the score value tflags BL_COUNTRY_RU_1 net describe BL_COUNTRY_BR_1 Mail client in Brasil header BL_COUNTRY_BR_1 eval:check_rbl('Brasil', 'br.countries.nerd.dk') score BL_COUNTRY_BR_1 2.0 # please adjust the score value tflags BL_COUNTRY_BR_1 net describe BL_COUNTRY_CN_1 Mail client in China header BL_COUNTRY_CN_1 eval:check_rbl('China', 'cn.countries.nerd.dk') score BL_COUNTRY_CN_1 2.0 # please adjust the score value tflags BL_COUNTRY_CN_1 net
complete nerds.cf to be copied to .\etc\spamassassin, uncomment the country and adjust the score for countries you want to tag as SPAM
More information: http://countries.nerd.dk/