Hey,
I think I've figured out a little temporary work around for all the Kayako spam every one gets.
In cPanel, go to Account level filtering -> New filter. In the first box, select "Spam status" and in the box next to it select "begins with". Then in the box below enter the rule "Yes". See the pic below:
Redirect all the spam to a Spam department within your Kayako system. This will let you review all the spam, just incase a client is marked as spam by mistake. Then from there, you can ban and delete the tickets that are actually spam.
Regards,
Sohan Tanna.