Setting up Site-Wide Bayesian Filtering

In local.cf, tell SpamAssassin where to find the Bayesian database files:

bayes_path /etc/mail/spamassassin/bayes

This tells the system that the Bayesian filter database files will be /etc/mail/spamassassin/bayes_msgcount, _seen and _toks. Feel free to move it wherever you want.

Now start feeding the Bayesian filter spam and ham messages. Tell sa-learn to use /etc/mail/spamassassin as the configuration directory (i.e. where to find the bayes_msgcount, _seen and _toks files):

sa-learn --spam -C /etc/mail/spamassassin --showdots --dir /path/to/directory/full/of/spam/msgs

sa-learn --ham -C /etc/mail/spamassassin --showdots --dir /path/to/directory/full/of/ham/msgs

Also restart spamd if you're running it already so that it will re-read local.cf and enable the Bayes filter:

ps axo %p%a | awk '/spamd/ { print $1 }'

spamd -x -q -d -L -u nobody

(your spamd options may be different than mine)