I released a new version, that now features :

* privileges drop (runs as nobody:nogroup by default)
* logging facilities (you know which r[h]bl was positive when a mail is flagged as Dirty)

I simlpified the code a bit, and made a debian packages on :
deb http://opensource.polytechnique.org/debian ./

I use it on my mail server since yesterday, and it works like a charm

For those that like the sources, go to my hacks page.
To build it, you need ocaml and the syslog lib (libsyslog-ocaml-dev in debian).