I've gotten spamcop block notifications a couple times in the last month or so. 550-"JunkMail rejected - lpmail03.lunariffic.com [188.8.131.52]:35386 is in an 550 RBL I called my hosting company's tech support line and was told that there are possibly thousands of domains that might be assigned to the same mail server IP address and when spamcop blocks the IP address, all of the users of that mail server IP address get blocked. Here I am, an innocent bystander... I'm the holder of my domain registration and the only user. The fault is apparently due to some other domain that just happens to be hosted by the same company and thus it's assigned the same IP address as the mail server for my own domain. So apparently possibly tens of thousands of innocent bystanders like me get blocked because of this system design. Is there no way to build a system more granular than that?