Scan Incomming POP Mail And Quarantine specific attachments

We receive mail via POP and I would like to content manage all incoming POP traffic

I do not want to use an email server on my network all users get mail directly to thier PC’s

We also send mail via multiple accounts and domain

Maybe some sort of gateway software that can sit between my clients and the router or alternatively a solution that i can Add with my SBS Server 2003 Prem with ISA Firewall