The workaround didn't work for me, formail just doesn't responds.
I found this script:
http://www.amavis.org/contrib/furio.infect
I had to add this lines at the top of the quarantined mail
X-Quarantined-From: <sender@domain.com>
X-Quarantined-To: <recipient@domain.com>
and then
./infect /opt/zimbra/amavisd/quarantine/virus-?????
this works for me