How can I do RBL blocking in exim rather than having MailScanner check for RBL listing?

You can block RBL-listed IP addresses directly in exim rather than having these mails processed by MailScanner. This will move RBL checking from MailScanner to exim which should help reduce server load. Emails from RBL-listed hosts will be completely blocked at exim rather than tagged as spam and delivered by MailScanner. You should use caution if you have users on ISPs that tend to get their IP addresses listed in these RBLs, as their mail will be blocked.

1. Go to WHM »Service Configuration »Exim Configuration Manager > Basic Editor > RBLs. Check your choice of the boxes for RBLs such as bl.spamcop.net or zen.spamhaus.org. Scroll down and click Save. Watch the output to make sure exim restarted successfully without errors.

2. Go to WHM > ConfigServer MailScanner FE > MailScanner Configuration and find the setting "Spam List =". Clear out that field so it is blank, and click Change.

After doing the above steps you should tail the maillog and exim_mainlog to ensure that both exim and mailscanner are working correctly.

tail -f /var/log/exim_mainlog 

tail -f /var/log/maillog