I would go with option 3 - send and receive directly from your trusted external partner, message labs. The only benefit to having a DMZ based relay is that you don't have to open tcp25 to/from your trusted network to the outside vendor. Not sure there is enough of a risk there to warrant a DMZ approach.
ISA is capable of proxying the SMTP conversation, but in this case it's likely just more complexity - can't KISS it. DMZ relays are useful as I mentioned above: if you need to isolate communications from your internal network to/from outside connections to help you manage hack attacks. But in this case, you only get mail from a trusted/semi-trusted partner. There is no "outside" or "untrusted/trusted" networks. The only thing you get with a DMZ host is added complexity and management of infrastructure. FWIW, ISA is useful for publishing OWA and so on. I could see that happening quite easily and fully recommend it where possible. Al On 12/5/06, Mark Parris <[EMAIL PROTECTED]> wrote:
A friend of mine has asked me to ask the group the following Exchange related question. An Exchange 2003 environment that has been upgraded from Exchange 2000 needs to have SMTP reconfigured for outbound mail. There are two proposals on the table but they are not sure of the best approach. 1 Exchange Frontend/Backend configuration with both servers on the internal network and an ISA server in the perimeter network publishing internal SMTP to the internet or in this case messagelabs or 2 Exchange Frontend/Backend configuration with both servers on the internal network and an SMTP server in the DMZ relaying to messagelabs Messagelabs host the MX records and cleanses most viruses out of the emails but may change in the future though there is no current managment thinking to do so. Given these two scenarios which one would most people choose and if so why? The environment is approx 2000 users and there are eight sites and the chosen SMTP configuration will be repeated in another site for resilience. Many thanks as always, Regards, Mark Parris Base IT Ltd Active Directory Consultancy Tel +44(0)7801 690596
