This is an example of a backend component of 'sought' rule generation.  It's
disk-space and CPU-hungry, and requires access to readable copies of your mail
corpora, so is best run offline, on a firewalled machine.  You can then publish
the results to the "sa-update" HTTP and DNS hosting machine via SSH, where you
then publish the update using the scripts in "mkzone_remote_svn" or "mkzone".

See "run" for the overall run script, typically run from cron.  Lots of hand-tweaking
for your setup will be required to adapt this.