I'm running exchange 5.5 and actually looking to switch to a Cisco firewall. I know that when I setup my firewall to allow exchange, I checked the microsoft knowledge base and used the following article to force certain ports for client access. You may want to read:
Fyi...This article is referring to making Exchange available to the internet in the context of Outlook access, not transporting e-mail. To send and receive e-mail you only need port 25 open and mapped to the correct private IP address. I don't recommend anyone to allow direct access to Exchange services from the Internet. Instead, a VPN is a better solution.
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...