Overview

You would like to know if Kerio recommends a particular blacklist.

Information

Kerio does not have a preferred blacklist. 

It is recommended to tag all emails from senders that are part of any blacklist. If you feel that a legitimate user is being marked as spam, you can simply add an exclusion for them in the Custom Rules section as mentioned in Excluding an Email Address From a Blacklist​​.

Further details on blacklists and whitelists can be found in the article Email Spam Protection using Blacklists and Whitelists.