finally I have resolved my problem... after 4 day...
I have a Debian Sarge server and I have installed the last stable amavis-new
from debian repository.
On this debian version (amavisd-new-2.4.1 (20060508)), the amavisd.conf file is ignored. All configuration need to be made in the files in the "/etc/amavis/conf.d/"
In the "/etc/amavis/conf.d/15-content_filter_mode"
file, I have removed the #
on the two lines @bypass_virus_checks_maps
Now all work.
I need only to check in the 20-debian_defaults
if all settings are good and properly configurated for my system.
The next time will be better to read the documentation well before beginning…
I hope this can help if anyone has the same problem.
(perhaps it is the case to point out it in the guide)