I am working with an ASA 5520 with a SPAM appliance located within the DMZ. Not all smtp connections are being corrupted by the inspect esmtp setting, just a few. It was discovered that those few sites that are connecting to the SPAM appliance traverse 2 additional firewalls (1 ASA and 1 PIX), *before* their smtp traffic hits the Internet to continue on to our DMZ.
Why would this be the case? Is it due to passing through two additional firewalls that may be adjusting the headers (static NAT, etc.)?
If we are not comfortable turning off the inspect esmtp setting, is it possible to write a specific policy that would include these few sites MX records? If so, how might that be done?
Table of ContentsIntroductionVersion HistoryPossible Future
UpdatesDocuments PurposeNAT Operation in ASA 8.3+ SectionsRule Types
Network Object NATTwice NAT / Manual NATRule Types used per SectionNAT
Types used with Twice NAT / Manual NAT and Network Obje...
Table of Contents Introduction:This document describes details on how
NAT-T works. Background: ESP encrypts all critical information,
encapsulating the entire inner TCP/UDP datagram within an ESP header.
ESP is an IP protocol in the same sense that TCP an...