Marc, First, you should make a design decision up front... Are you going to allow IP addresses of valid hotmail and yahoo DNS servers (for example) which spew out a very high percentage of spams (especially nigeria scams) on your list, or not?
Personally, I think that it is better to NOT try to catch these via RBLs even if only a tiny percentage of mail from some of those IPs is legit. Therefore, IMHO, a good RBL will try to whitelist frequently used valid SMTP servers up front to prevent such collateral damage. I thank God that many RBLs do NOT do this and many ISPs use such RBLs... this causes collateral damage which then puts pressure on these ISPs to clean up their acts... but I just don't want that collateral damage on MY server. Finally, one really great resource for getting info on valid DNS servers is: http://www.senderbase.org/ For example, if you enter the IP address of a valid SMTP server, it usually returns this IP and OTHER IP address from that same organization. Keep in mind that being listed on serverbase.org alone doesn't mean that the IP isn't a spammer's IP... but if senderbase reports the IP as belonging to a legit organization and as being frequently used, that might be a good IP address (or IP address range) for whitelisting to prevent it from ever showing up on your RBL. Rob McEwen PowerView Systems [EMAIL PROTECTED]
