as stated burleyman, the ASA need to be "Trusted Sender" from the perspective of the SMTP Server, if you had an Exchange Server then add the ASA IP Address to their trusted address if you had Linux Server, same issue.
This is what i though about the problem.
had a great day.
had a great day .
best regards, and rate if you'll find this post useful
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...