Try the modified configuration (attached) - I have included only www and smtp access. By defult the PIX will allow all connection outbound (Higher Security Interface to Lower Security Interface) but if you need any services such as smtp/www allowed into your internal network then you'll need ACL and static for this process.
Make sure that your MX record is pointing to the correct public IP address which is bound to the outside interface for smtp also for www access.
Also, note - if you only have the one public IP address and this is being used by the outside interface then you can substitute the ACLs and statics as such:
access-list outside_in permit tcp any host 22.214.171.124 eq smtp
access-list outside_in permit tcp any host 126.96.36.199 eq www
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...