Ignition 7.6.5 - AD/Internal Hybrid Problem

Hello
I have just defined a new AD/Internal Hybrid user source profile.
I have configured it as shown in the attached image to connect to a Windows 2008 AD Controller, but I can’t see any AD user in the Manage Users window.

Log messages show the error below:

AD_Internal_Hybrid [profileName=NewProfile] Error finding users.

javax.naming.PartialResultException [Root exception is javax.naming.CommunicationException: mydomain.local:389 [Root exception is java.net.UnknownHostException: mydomain.local]]
Caused by: javax.naming.CommunicationException: mydomain.local:389 [Root exception is java.net.UnknownHostException: mydomain.local]
Caused by: java.net.UnknownHostException: mydomain.local

I would point out that the server running Ignition is not member of the AD: is it necessary?
Can it browse AD users without being a member of the domain?

Many thanks
Claudio