BES in an izolated enviroment

[waces]

Hello,

I'm currently runs a BES server in my enviroment without any issues. I received a request from our developer that they want to test some issues with their products and requested a separated BES enviroment.
I created a small and separated domain for this with a DC for AD, Exchange 2007 with OWA and 2 BES servers (4.1 and 5). That domain are able to access the internet.
OTA activation failed. It should be proveder related. But activating via Desktop Manager and USB-connected BB handheld also failed and I can't figured out what can cause this issue.
The user on BB is valid in the domain, exchange and added as user for BES. OWA for the user works. Inter-site mail sending works withouit any issues.

I'll be very thankful for every ideas you come up.