"FloodGuard" . I don't know if it would help in this case, but it wouldn't hurt to take a look at it.
This software/hardware wouldn't provide us any benefit because it would have to be installed at the Tier-1 providers (AT&T, Sprint, MCI, Level 3, UUNET, etc...) to be of any use over what we are doing now.
As I said all support tickets have been answered. Did you get the automated response with the ticket number? If so, twhat's the number?
Also if you are unfortunate enough to be using AOL as a provider, you will find that they are automatically putting all emails from our server into a Spam folder. You might want to check this out.
The IP router blockage does not affect outgoing email at all. More than likely your email client or ISP (in particularly AOL) is tagging email from our server's PHP scripts as spam.