1) the ESA handles so much mail that tracking data can not hold enough historical data on the system to return any search results
2) the search is perhaps malformed or incorrect and not returning any data.
in any case - check your mail_logs for a definitive answer. if the time doesn't go far back enough - copy the logs through FTP / SCP to another box and you use your own parsing tools to look through the data off-box.
if you can include anything you have from the mail_logs then i'm sure we can help.
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...