554 DHCP Pool clients should use their ISP's mail server
Tailing my mail.log, it sure is rejecting a shitload of messages!
But really, you shouldn't be running an MTA on your DHCP address anyway. I know this will block some geeks who just want to run their own mail server, but they should be smarthosting it elsewhere.
Next step: ClamAV? That's the one you recommended, right scsi?