Better antivirus (AV) protection?

[Damian]

> Yet, we are recently receiving a lot of mails with virus-infected 
> attachments (usually in 7z files) which are scanned by amavis/clamav 
> but are NOT getting detected. 

How do you know that they are infected? Is your setup not detecting 
those viruses because neither Amavis nor ClamAV look inside the 7z 
archive, or because ClamAV has no signatures for them?