I used ZAF, ZAP, ZASS but found they didn't provide adequate logging or display insight into what was happening or how things should be configured. One use of a firewall is for figuring out what should/shouldn't have been blocked/allowed, and ZA never really helped me. But try the newest ZAF and see if it suits you. I am trying out Kerio 2.1.5, and so far seems fine. Like the KPF4 GUI, but don't understand the startup problem at all. Must be a conflict with something, but I don't have a complicated system and don't see any effort on the Kerio forum to help solve the previous comments on it.