Exchange providing wrong external IP in message headers

[James Bond]

When a user from my network sends email outbound, the header contains the wrong external IP. This is causing Reverse DNS to fail, and is causing some major issues.

I have a NAT statement set up on my edge router to NAT the internal address of the Barracuda to the correct external IP...

Anyone have any clue as to what could be causing this?

 

[spidey07]

SMTP provides the sending mail server's IP address in layer7. You can't use NAT unless your nat device is smart enough to change the IP address in L7. Any firewall and most commercial routers provide this feature.

 

[James Bond]

Originally posted by: spidey07
SMTP provides the sending mail server's IP address in layer7. You can't use NAT unless your nat device is smart enough to change the IP address in L7. Any firewall and most commercial routers provide this feature.

Sorry I wasn't more clear -- There is a firewall. Should I just be using a regular NAT statement?

 

[spidey07]

What is the device doing the NAT? This device needs the ability to understand there is SMTP running on tcp port 25.

If you just do regular nat it is going to break it. Depending on the firewall you'll have to let it understand that you're natting SMTP on port 25.

 

[James Bond]

ip nat inside source static tcp 10.100.0.121 25 xx.xx.xx.xx 25 extendable

xx.xx.xx.xx=correct external ip
10.100.0.121=barracuda

 

[err]

are you using your barracuda as outbound smtp relay? If yes, then the RDNS needs to be created for barracuda, instead of your exchange box.

You also have to make sure your exchange uses the barracuda as its smtp forwarder (in exch2007, its under smtp send connector)

I never have problem with exchange relaying the email through other smtp boxes.