Question : Windows 2003 SMTP Relay in a DMZ

How do I configure the networking for a SMTP Relay in a DMZ?  My DMZ sits behind a Cisco Pix 515.  As I see it I have 2 options.

1.  Either having 2 NIC, one to the DMZ and on the LAN?
2.  or set up routing rules and allow incoming and outgoing SMTP traffic on the PIX from the internet to the SMTP DMZ server and from the SMTP DMZ server to the LAN (Exchange Server).

Setting up the SMTP service (IIS, etc) should not be an issue but I'm unsure on the network setup.  I did try to setup the first senario but as soon as I set up the second nic (eather to the DMS or the Lan) I lose connectivity.

Thanks!!!

Answer : Windows 2003 SMTP Relay in a DMZ

>>then it is now part of your internal network and not part of the LAN
should have been
then it is now part of your internal network and not part of the DMZ