MS DNS and BIND DNS

[sharun]

Hi,

Before I lay out my question(s), I would like to explain
the situation first.

- Our company is using both DNS types: Microsoft and BIND (8.1.2).
- We have two DNS servers: inside and outside the firewall.
- The problem(s):

	1. When we use BIND DNS, and set our server to external
	   DNS server, we have no problem resolving any site
	   (internal and external). We have no problem also when
	   we use default DNS server (which is inside the firewall).

	2. When we use Microsoft DNS, and set our server to external
	   DNS server, we cannot resolve (inside and outside). But,
	   when we point it to our internal DNS server, it has no
	   problem.

	3. When we point it to our internal ip of the firewall, it 
	   works fine.

Does any of you have any idea why this is happening? Sorry, I'm new
in DNS stuffs. By the way, one important note: we point our Microsoft
DNS server to BIND DNS server (in cases 1 and 2). 

Thanks in advance.
Ridhuan.