I have written a collection of scripts to prevent massive cross-postings
to smartlist-managed lists, so that they are directed to /dev/null
(not recommended), archived, moderated, or whatever.
Crossassassin version 0 is available here:
deb http://people.debian.org/~sanvila/debian woody main
deb-src http://people.debian.org/~sanvila/debian woody main
The user decides about what to call "massive". The default value is 5
lists or more, but nothing in the package is set in stone.
The package is very simple and it's made of shell scripting, formail -I "",
md5sum, queues, cron jobs, awk, and procmail rules, which are the
tools I'm familiar with.
Feel free to rewrite it in your language of choice if you don't like it.