Question : Exchange server sending emails through NAT Address

We recently changed our Exchange Server to use DNS to route to each address space instead of forwarding mail to a smart host.

Since then some emails have been successfully received and others not.  (we are receiving all emails)  From the Non-Delivered Report, I can see that emails are being sent from the IP Address of our ISA Server and not the External IP address we have set for the Exchange Server.

In ISA Management, we have set Server Publishing rules for SMTP Server and POP3 Server, mapping the correct internal address and external address for each.

The External address for the Exchange server is one of the multiple addresses added to the north-bound NIC.  This is the address in our MX record.  

I'm obviously missing something.  Can any of you help me get our Exchange server to send to the right address?

Any help is much appreciated.

Thanks,

tom555

Answer : Exchange server sending emails through NAT Address

OK ... so do you have two (or a block of) external IP addresses?

Your outgoing traffic from the mail server, if it passes through the ISA server, will appear to come from the ISA server itself.  As DCMBS says, you will need to NAT directly via the router, which means you will not be able to use the ISA server to publish your mail server.

I'm not sure how you have mapped the mail server to .210 using ISA server.

Either change the MX record to .211 or, if you have two external IPs, bypass the ISA server by assigning the default gateway of the mail server to the router and use the router to publish the mail server.