access external email through SBS

[somcs]

Ok I'm getting pretty frustrated at the moment. Having a problem with external email. Our old network used to look like this


192.168.x.x 192.168.x.x
Internet -- ADSL modem -- Router -- SBS Server
192.168.x.x
-- Users

Internal email handled by Exchange Server on SBS (2000) acessed with Outlook. External email hosted by ISP. External email accessed with Outlook Express set to use the same internet connection as IE.
So I have just changed it to

192.168.x.x 192.168.x.x
Internet -- ADSL -- router -- SBS Server
|
10.0.x.x
Switch
|
users
10.0.x.x



Now internal email works fine (exchange), and people can access the internet with IE. The problem is that no one can access their external email. I am using ISA server. I have changed the firewall rules back to allow all so its not the rules. Its not on the ISP's end as I can access email through a web terminal, and if a laptop uses a dial up connection they can get external email. I am running out of ideas.

I currently do not want to configure the exchange server to handle external email.


thanks for any help

james