Stephen Downes asked why he can’t tell his computer that all emails in Russian are spam. Here is my answer.
Part 1. Selecting emails per language
As far as I know, this is not a documented feature, but GMail allows you to select emails per language. Just type in the search box:
(I am aware the Chinese is not a language.)
You can also type “lang:chinese” if you prefer instead of “language:chinese”.
It has both false positives and false negatives. For example, I got an email with the subject line “L’internationalisation V.S. le SEO” which is clearly in French… but GMail fails to recognize it as French.
Part 2. Getting the spam filters to listen to your preferences
See my post My spam filter is asocial.