POP3 Virus Scanner Proxy is a full-transparent proxy daemon which scans all mails for viruses using third party scanners (built-in support for AVPD and Trophie).

You have to set up a port redirection in the linux-netfilter (iptables) so that all connections from e.g. inside your office to any POP3 server outside in the world will not leave your router, but come a local port, on which POP3VScan listens. POP3VScan receives from the linux kernel the original destinations of packets (the POP3 server outside in the world) and will connect to them.

All data we receive from the client will be sent to the server, and vice versa. With a little enhancement: we parse the neccessary parts of the POP3 protocol and when an email is sent from the server, we store it into a file, invoke a virusscanner and send it if it is good, or we just replace it with a virus notification. It should be possible to use all scanners using the scannertype=basic. Also POP3VScan provides scannertype=avpd for high-speed scanning using 'Kaspersky Anti-Virus for Linux', every C programmer can easily adept other scan-daemons (trophie, sophie, antivir, ...).

Neither the client nor the server has to be configured, none of them will take notice that there's a mailscanner (except the client when he gets a virus notification or if he looks into the header, and the server gets our ip as source).