Server behind a firewall
Question asked by Sean Middlemore - 7/6/2016 at 6:29 AM
Hi everyone,
I'm about to move my current 800+ SmarterMail user base to a new server which is behind a Cisco firewall and a slightly different IP address setup. I've noticed that the server itself can't see the external IP address that is used to access it but rather its internal one that the external traffic is sent to. Is this likely to cause a problem when I move everyone across? I've setup SmarterMail on it and can access it via webmail no problem.
The IP address setup is something like this:
External                Internal
I've setup the IP address bindings to and the hostings to be external IP.

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Merle Wait Replied
If it is behind a firewall... then you have to:
a.) bind the server to internal I/P address.
b.) make sure that the appropriate ports are open on the router.
c.) If you are sending emails out... AND the server is supposed to be the sending MX server,
    then you need to make sure that you are not going to pick up the router's address but the actual external I/P address for the server.   Not sure how you do this in CISCO, but in our routers I have to tell it to "preserve" outbound email address.
Finally, although your server doesn't  "itself" use the external I/P address, anything inside the firewall.. should still be able to resolve the external address.
Sean Middlemore Replied
Hi Merle, My managed host provider has confirmed that it has all this so should be good! Thanks for your help.


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