Maybe there is a rule that I'm not aware of so here I am. I was previously using my mail server behind my ISA server which in turn had a direct(real) IP. This same IP has an MX record as pointing to my mail server and once mails hit my ISA , the ISA redirects ports 110,25 & 80 for the WEb access to the Mail server.
Now I am introducing an ASA5520 and I tried to put another REAL ip in the range for my external interface while creating a Static Nat for my REAL (MXed) IP , but that just doesnt seem to be working.
Basically unless my MXed IP is on a physical interface ( like NIC of server or Outside of ASA) , i cannot ping it. IF i position this MXed IP on the outside interface and then try a static nat for any of the other IPs in the range, it works just fine..weird aint it ???