Lately the amount of spam with russian encoding/charset that I was getting had increased significantly. Spamassassin’s configuration options “ok_locales” and “ok_languages” were not enough because I didn’t want to whitelist some language, but I just wanted to blacklist some.
So the solution is to create a custom rule file by loggin in as root.
For example create /etc/mail/spamassassin/myrules.cf and insert the following lines:
header LOCAL_CHARSET_RUSSIAN Subject:raw =~/\=\?koi8-r\?/i
score LOCAL_CHARSET_RUSSIAN 7
describe LOCAL_CHARSET_RUSSIAN Contains russian charset that is not acceptable
If you want to add even more charsets:
header LOCAL_CHARSET_BLOCKED Subject:raw =~/\=\?(koi8-r|windows-1251)\?/i
score LOCAL_CHARSET_BLOCKED 5
describe LOCAL_CHARSET_BLOCKED Contains charsets that are not acceptable
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