Just set up a SME server with an SMTP proxying firewall. So all the POP3 connections appear to come from 10.0.0.5 (the proxy). This causes a deny
2006-03-08 07:05:32.850267500 tcpsvd: info: concurrency 5578 10.0.0.1 1/4
2006-03-08 07:05:32.850270500 tcpsvd: info: deny 5578 0:10.0.0.5 ::10.0.0.1:59956 ./peers/10.0.0.1
2006-03-08 07:05:32.850353500 tcpsvd: info: end 5578 exit 100
2006-03-08 07:05:32.850370500 tcpsvd: info: status 0/40
I know where to set this for IMAP, but what about POP3