In ,
Dinendra typed:
We have a Exchange 2003 server which is accessed by corporate user in
exchange mode (RPC)

(I think you mean MAPI here)

in the LAN. Some of these users need to access
the server remotely by dialup to the corporate RAS server using the
smart client (MS Outlook 2003 - Exchnage mode).

RAS? Dialup? Golly, I haven't heard that term in years. This is not going to
be much fun for them. VPN over broadband isn't an option?

There is a Firewall
sit in between the RAS and the exchange server. RAS is in a DMZ
network and the Exchange is in the trusted network. What are the
ports required to be open between the RAS and the Exchange server in
order to access the exchange server in a secure manner.

Please advice

Have you considered using RPC over HTTPs instead of all this? That would be
sooo much better. If you're already allowing users to check OWA with SSL,
you don't need to open any additional ports. And if you're concerned about
security, a FE/BE config and ISA will go a long way....and still let your
users connect using RPC over HTTP.

Anyway, this isn't really the right group for your question, as it's about
networking, and has nothing to do with Outlook per se. I don't know what
you've got open between DMZ and LAN right now, but they'll need TCP 135, 139
at a minimum. You should post in an Exchange group for more help.....try
microsoft.public.exchange.connectivity. Good luck!