If I understand you correctly, you have placed Astaro behind an IPCOP firewall already.

I think you need a Packet Filter Rule set to solve your problem.
By default, traffic from the internal to the external network is not allowed.

This is what's required to have ALL protocols allowed FROM the internal network TO the external network.

First, the definition of the secure network. go to Definitions - Networks and define a network (I call it LAN) for instance with IP 192.168.100.0 and MASK 255.255.255.0

Then the trick.. you need to open for ANY service to ANY server... go to Packet Filter - Rules and add a rule FROM LAN, service ANY, to ANY (allow)

I hope this works for you. Also remember that ASL's default gateway MUST be the IPCOP machine.

Best regards,
Ørjan Sandland