ClamAV is letting hundreds of infected files thru every day. It no longer seems to be able to scan attachments inside .eml file format (neither will Microsoft Security Essentials). F-Prot will and it's reasonably priced. I have done quite a few tests on infected .eml files and find F-Prot is the most reasonable way to go, and ClamAV is nearly useless. I can provide an example if you post an email address I'll send them to you.
What I need to know is if anyone has the proper current F-Prot command line syntax. I used to use it, but have lost my notes. It was on the old forums here, but that data is gone as well.