RBL stands for Realtime Black lists and it mainly works for email servers. RBL is a collections of IP addresses or network addresses which has been found to be spamming. So the email servers will connect to these RBLs before accepting email from an IP and make sure that the IP from with the mail arrives is free from spams.
It has been a proven way to reduce in coming spams, but there can be some false positives. To add a custom RBL in your email server can be cumbersome and email server config file can hurt your brain. But cPanel have a fully integrated web interface, in which we can perform a lot of customization and control how the mail server works in cPanel.
cPanel comes with spamcop and spamhaus RBLs and most of the time they are fair enough. If you want to add a custom RBL. you need to navigate to Main >> Service Configuration >> Exim Configuration Editor >> RBL
and then click on the manage.
Then you will be presented with a page like this and here you need to enter the RBL details which then will be saved to the exim configuration file. Make sure that you wont edit the changes via the configuration file via SSH. cPanel will reset it.
- Rbl Name: the name for referrence
- Rbl Info URL: the url that shows up in bounce messages
- DNS list: The lookup URL of the BlackList
You can consider http://www.dnsbl.info/dnsbl-list.php if you wish to have custom RBLs in your server. You need to do this at your own risk – because we are not sure how active those lists are and some of them even ask a fee to get IPs delisted. Further, your email server can stop working if any of the RBL you have configured has stopped working.