Let me explain our scenario.
1. we have one Router and one PIX. Router is connected to the internet. And PIX is connected to inside.
First I configured Router ann it was fine. We could browse to the internet and there is one email server at inside of Router. And the Email Server is working fine. We have 2 Public IP Addess, one we used for router outside and other we used as NAT for email server.
2. Now we connected PIX 515 at inside of Router. Ans we used private IP address for router inside and pix outside. We did NAT at PIX (private to private) and we can get access to internet.
We also did NAT for email server private IP address to Public address. We also configure access list for outside to inside. But we can not get access to Email Server that is in inside. We used this before that time we used to have public IP for PIX outside.
Appreciate you expert suggection.