how to pass infected attachment

[Володя К. via amavis-users]

>
> amavisd-new does not drop attachments (unless you've installed and
> enabled/configured the optional altermime module).
>
> Most likely something else is dropping the attachment after amavisd
> sees it. Commonly desktop antivirus or a firewall is the culprit.
>

strange I have no local anti-virus , no firewall (I have ubuntu os).
If I disable the amavisd(+clamav), the infected email is successfully delivered, so there is no problem on my local computer.. This is clearly a server-side.