hi mohana
urs works but i suggest u to make the ASA the edge device with the internet
and the ISA will be behind the ASA and the DMZ will be the network between the ASA and ISA
like
lan--isa--mailserver---asa--internet
this if u want those servers to be accessable from internet as well
or u can make it like
lan--isa-----asa--internet
--
-- servers DMZ
or
the DMZ on the ASA if u want the internet users to access these servers
all works but becarefull with NATing and the packet filltering inbound and outbound
good luck
if helpful Rate
