To detect spam when visiting a group, set the group's
spam-autodetect and
spam-autodetect-methods group parameters. These are
accessible with G c or G p, as usual (see
Group
Parameters).
You should set the spam-use-* variables for
whatever spam back ends you intend to use. The reason is that
when loading spam.el, some
conditional loading is done depending on what
spam-use-xyz variables you have set.
By default, only unseen articles are processed for spam. You
can force Gnus to recheck all messages in the group by setting
the variable spam-autodetect-recheck-messages to
t.
If you use the spam-autodetect method of checking
for spam, you can specify different spam detection methods for
different groups. For instance, the ‘ding’ group may have
spam-use-BBDB as the autodetection method, while the
‘suspect’
group may have the spam-use-blacklist and
spam-use-bogofilter methods enabled. Unlike with
spam-split, you don't have any control over the
sequence of checks, but this is probably
unimportant.