It has been said before but I still would appreciate it very much if ISP's would only allow SMTP traffic to go through the provider's mail-servers, not directly from dsl/cable to the Internet. It would stop most spam/viruses from infected systems.
Even better, block but provide a web page to unblock. Anyone savvy enough to navigate the web page has a good chance of being competent to use direct-to-MX (not to be confused with "running a mail server").
