Actually they are not able to receive the mails from outsidedomain like yahoo.com or rediff.com etc.
And they have installed solution on their exchage i.e. mail security for exchange with has built in antispam.
You mean the guys who're rejecting your mail can't receive mail from the outside? Sounds like a blacklist issue on their end, not much you can do other than somehow let them know that their mail relays are being "unreasonable" with their blacklisting.
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...