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