>If we were place our new email server behind a secure NAT, I assume all
>incoming emails will process okay, because of the external to internal NAT
>translation...
>
>My question is; isnt all outgoing email suppose to also be sent from the
>same IP address as specified from the MX record? or is the external IP
>from the firewall okay?
The external IP from the firewall *is* your MX record. :)
Internally, your mailserver has a private IP, such as 192.168.0.1. That's
all it knows about. When it sends an E-mail to another server
(mail.declude.com for example), the firewall translates the 192.168.0.1 to
your public IP address. When mail.declude.com sends you mail back, it
looks up your MX record, which leads us to your public IP address. Your
firewall then translates that public IP address back to 192.168.0.1. So
mail.declude.com has no clue that your mailserver thinks that it is
anything but 192.168.0.1.
>The reason is, I want to move our existing email server from the exposed
>internet (running a s/w firewall) behind a h/w firewall. I'm just afraid
>that all outgoing emails will be rejecting because our MX record and all
>outgoiing traffic through the firewall will not be the same...
No, that won't be a problem. Even if the IP was different, there wouldn't
be a problem (for example, if you have IMGate set up, you may have IMail
send directly to the world, even though the MX records point to IMGate).
-Scott
---
Declude: Anti-virus, Anti-spam and Anti-hijacking solutions for
IMail. http://www.declude.com
---
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