GFI mail essentials,& Netshield ?

Well, the answer to your question depends on a bunch of technicalities, (as an example, packet spoofing, IP address cloning, processor ID masking, using someone else's email server to send viruses) and if you get the sending IP address off the packets, one is not sure that is the correct address (see above). Hackers, virus makers have gotten very very tricky in how they work (except for their connection and identity to their ISP and even then, masking their processor and board ID makes that waya dead end. Some use dialup connections from a laptop from a hotel room under a false name and account, stolen credit card which makes even that almost impossible to get a track on where the virus came from). Verizon telephone company is in a lawsuit right now on what law requirement there is and their legal responsibility to have to reveal who (source) sends spam email(which also includes revealing infected email sent by one of their users). There are ways to intercept and track back to the actual physical source location, packets in transit, much like tracing a phone call but that is for active connections not spoofed packet email from a email server that has been hacked into and used to send out viruses.