Publishing Exchanging in ISA 2000 server

I would like to have some advices regarding our DMZ design. The following is the setup

                                              Outside to DMZ(25, 80, 443)
Internet (Outside)----------- PIX --------------------------------(DMZ) {AntiSpam, DNS, Web}
Outside to Inside (80, 110)   -        DMZ To Inside (25, 1433)
                  ISA Server {Published Server: SQL,
        Front-End Exchange 2003(POP3, SMTP, OWA, OMA)}

I would like to know what are the threats by having the POP3 & OWA traffc reaching the inside network as the Fron-End exchange is Published in the ISA server. ?

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Hi mofne,
The threat is that if there are any vulnerabilities in those services someone could gain access to that machine and from there your entire network.
It would be better to locate the exchange server in the DMZ as ideally you don't want to be redirecting any ports to the inside network. This does mean that the exchange server has to be independant of your internal domain though.
mofneAuthor Commented:
we design the DMZ like this to eliminate opening ports in the ISA server,
for the frond-end exchange to communicate with the back-end exchange server and
the AD for the authentication. If we put the front-end exchange In the DMZ and it been
Compromised the attacker can gain access to the inside network as well

So what other scenarios so you recommend,  thanx  alot for your comments

What I would do is move the Exchange server into the DMZ so that no ports need to be redirected to the internal network.
However this does mean that the exchange server will have to be configured as a standalone server or in a separate domain by itself since you don't want to allow it to talk to the internal AD controller.
It would be better to actually have the Exchange server(s) on a second DMZ interface so that you can firewall between the web server and Exchange since most of the security volnerabilities are with IIS.

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mofneAuthor Commented:
thax again,,
Well i never heard of putting Exchange in a separate domain ! but its interesting  i will read a bout it,

just to add something to the full picture, when i talk a bout the inside network here i'm taking about it from
the pix firewall, means the traffic is hitting the outside interface of the ISA, and as we consider the ISA
as the second level firewall.

Actually  im not convinced with this design but I’m tying to find out and highlight the threats, because
our Microsoft expertise see it like this and they introduce this solution to us. But still I didn’t get any
new idea about this issue,

Thanx alt for your help :)
mofneAuthor Commented:
Thanx jj2 alot for the helpfull links  
i think i will go through it it seems intresting :)
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