How to set up spam filtering with Bogofilter?

[Dmitry Dzhus <mail@sphinx.net.ru>]

Greetings!

What is a way to make Bogofilter installed on my machine help Gnus to
sort out spam mail?

I use a single nnimap mailbox called "INBOX" to read my mail.

I've set `nnimap-split-fancy` according to the docs (parts of code
stripped from customize section of my `.emacs.el`):

    (nnimap-split-rule (quote nnimap-split-fancy))
    (nnimap-split-fancy (quote (| (: spam-split) "INBOX")))

And actually turned on splitting for "INBOX" group:

    (nnimap-split-inbox (quote ("INBOX")))

Group to put posiible spam into:

    (spam-split-group "spam")

And I've pointed to Gnus to download message bodies so filter could
process them:

    (nnimap-split-download-body t)

I've also set `spam.el` to use bogofilter:

    (spam-use-bogofilter t)

Now when I see a spam message in my "INBOX" I press `S x` and see the
message marked as spam. When I quit the group I see Bogofilter
processing marked messages (it really does as I manually checked
bogofilter database file at `~/.bogofilter/wordlist.db`). 

When I make Gnus check for new message in my "INBOX" folder, I also
see Bogofilter processing downloaded message bodies, but still ALL
SPAM gets in my "INBOX" without any splitting at all. And also
checking «spamacity» score with `M x` gives the result of `0.5200000`
regardless of message contents (even if I had marked it as spam some
time before).

Bogofilter's wordlist database is quite big.

Seems that the problem might be connected with the fact that I use
nnimap method to read my inbox.

What could I also try to make Gnus work with Bogofilter properly?

-- 
Happy Hacking.

Dmitry "Sphinx" Dzhus
http://sphinx.net.ru