Hello, An RBL, a Realtime Blackhole List, is a service that lists the IP address of known spammers. Mail server administrators can then choose to use these lists on their server to block incoming connections from IP addresses suspected of being spam senders. One of the benefits of using an RBL is that you can block a potential spam at the IP connection level before you need to use a more resource program such as SpamAssassin to check the content of an e-mail for spam. I have used the Spamhaus RBL for many years now, and recently began also using the Barracuda BRBL. Which RBL's do you use?