Sorry for long time, little holidays
The problem is checked, I received again my logwatch mails : I've modified the /etc/amavis/conf.d/20-debian_defaults and added my domain to the read hash list, like uncleCameron, with -18
I've made the modification too, proposed here :
Clamav don't speak anymore in my logwatch to annonce his updates (freshclam), so I've just modified my freshclam.conf and putting true on the following options : LogVerbose true & LogSyslog true. Wait and see my tomorrow logwatch.
have a nice day !