We had a computer on the system infected, sending spam thru the server. We are not an open relay. Cleaned up the computers and switched to a smart host. All was fine until today, there are 90,000 emails in the queue folder on the server. the queue in Exchange only shows the smart host connector. This is Exchange SP2. I suspect another computer infected. There are using two nic's in the server, not ISA just Windows firewall. In addition to finding the infected system and cleaning it what else can I do?