Real-time blackhole list (RBL) is a list used by mail servers to identify email spammers. A RBL is an accumulation of IP addresses whose owners refuse to stop the dissemination of spam. Mail servers use this information to reduce spam in one of two ways:
- Marking the message as spam.
These are the emails you find in your junk/spam folder. - Not delivering the message.
These messages never make it to your email account.
The method chosen depends on which list(s) the IP address is associated with. Mail servers typically use a number RBLs.
RBLs are also know by the following names and are used interchangeably:
- Realtime Blacklist
- DNSBL – Domain Name System-based Blackhole List