Since e-mails are not only correctly directed to the intended addresses but the can and are also screened for a number of characteristics, why do ISPs and others not offer screening for viruses? I would be surprised if others would not be willing, as I am, to pay an increased subscription charge for such a service in preference to the bog-standard.
This is starting to happen with ISPs. My ISP is BTinternet and they started to offer virus scanning a few weeks back at no extra cost.
Its important to also have a virus scanner on your PC as well, as you may introduce a virus from a floppy disk or CD. Also a second virus check on incoming e-mail would be useful as no anti virus software is 100% effective.