Outlook thru a firewall (Exchange 2000)

I run an Exchange 2000 server behind a firewall.

I would like to try and open up ports on my FW to allow Outlook 2000 and XP users to access the server.

I have seen the documents that detail what registry keys to create for Exchange 5.5, but Ihave not seen any that explicitly mention E2K.

Are the registry keys the same? My system doesn't even have some of the higher-level subkeys:

System\CurrentControlSet\Services\MSExchangeDS\Parameters

System\CurrentControlSet\Services\MSExchangeIS\ParametersSystem

Do I need to create these subkeys too? Or are there different keys? Or will this not work in E2K?

Thanks!

Jed