Publishing exchange server on isa server 2006. INbound mail not workin

[windowsfan]

recently tried to publish exchange server through ISA Server 2006. I am not able to send email from external to internal SMTP Server.

This is my current configuration:
Cisco router-------old Checkpoint FW---------Exchange Server
Natting for Exchange
Wiith the above configuration email is working fine.

This is what I am trying (Inbound mail not working)
Cisco router-------ISA Server ( 3 NIC ,[INT,DMZ.EXT])----Exchange Server
I have three rule configured
Mail Server Publishing rule(InBound):Server to Server communication to Int IP address of Exchange Server and listening on Ext NIC of ISA server. (MX records points to Ext NIC IP address)
Access rule (SMTP Outbound) for outbound mail:
Mail Server Publishing rule: Allow Internal mail client to Exchange server (Outlook RPC) From Internal to Exchange Server.

What am I doing wrong and how should trouble shoot? I need some help, Please!

 

[mRgEE]

I am having the same problem at the minute and unfortunately haven't fixed it yet. However, I think that the problem may relate to NAT. I can see that your Checkpoint has Natting setup for Exchange. How is this setup? Do you perform any Nat from your router > firewall?

I also want to get to the bottom of this issue as it is driving me crazy at the min.

 

[windowsfan]

hi mRgEE,
I finally called MS and AT&T (ISP). This is what we found out. There were static route on Cisco Router going through old FW. I used old FW IP on the new FW and it started working.