[N3WBI3]

Instead of blocking port 25, I'd rather have my ISP use the Open Relay Database and other blacklists to block traffic coming from known zombie or spambot servers.

this is the problem, when you infect millions of desktop PC's an RBL is no longer going to work. Given the fact most high speed nets are DHCP you could find yourself blocked because the guy before you was a bot. If anything white list would work if not for the fact maintenance would be damn near impossible..

[TechJunkYard]

.. when you infect millions of desktop PC's an RBL is no longer going to work.

Yeah, they do. combined.njabl.org has a blacklist of DHCP addresses which is pretty darn complete.

Given the fact most high speed nets are DHCP you could find yourself blocked because the guy before you was a bot.

Not a problem. You use the "smart host" part of sendmail to send all outgoing mail to your ISP's SMTP server.