In order to have the outlook/exchange functionality, you must have successful name resolution via WINS (assuming we are talking about Windows NT and Exchange 5.5 or earlier) If your mail server is in the DMZ of your PIX, I would consider moving it to...
As far as I know the PIX is not capable of such a configuration. Besides, most internet providers will not route packets destined for addresses defined by RFC1918 (internal addresses).
