mail-filter/bogofilter-1.2.1-r1 supports tokyocabinet database backend with USE=tokyocabinet. As dev-db/tokyocabinet is currently not keyworded on your arches, your keyword was dropped. Testing bogofilter: FEATURES=test USE="-berkdb -sqlite tokyocabinet" emerge "=mail-filter/bogofilter-1.2.1-r1'
tokyocabinet use.masked, closing