I agree with werter, gerald_FS and gsiotas too
I use Zentyal since the "ebox time" (1.2).
I even tried to promote Zentyal to schools as an "all in one server" as it HAD a lot of network features
But with every new update the community release is trimmed. Over the time a lot of features disappeared (proxy, ids, wan failover, antivirus, web server, traffic shapping, events, Dynamic DNS etc)
Zentyal is still a great product, but not as a standalone server. Other servers are necessary even in a small network (10-20 computers and devices)
I will too, try to migrate to other more completed (of services) alternatives.
nethserver.org looks promising. It reminds me the reasons I choose Zentyal a few years ago.