My scenario is this :- Currently have our main site (offices)withone 5.5 Server andone new 2003 server. Our migration to fully 2003 is drawing close. The 5.5 server now only handles Internet mail and links to our factory where there is an old 5.5 server also. ADC is up and running perfectly and allis well.In the next couple of weeks our wan between the two sites will be upgraded to 10Mbits. I also have a brand new server ready to go to our factory with exchange 2003 and windows server 2003 ready to install. So the tasks I need to complete are :- Install the new server in our factory (at the other end of our wan) and then get rid of all of the 5.5 servers. I'd like to have the new 2003 server in the factory setup so that if the wan goes down they can still log onto their domain and work on their files etc and any emails they send would sit in the queue until the WAN is back up. This is what happens now in 5.5 between the two old servers. In the old 5.5 scenario they are in their own domain but are still within the organisation as far as Exchange is concerened. Is this still possible ? To seporate Domains and Active Directories but in the same exchange Organisation ? Or do I add their new server to our exisiting office domain as a domain controller ? As there are only a handful of users in the factory I intend on just moving their mailboxes the old fashioned way i.e. PST files and not connecting their old 5.5 server to the new 2003 server. I hope all of this makes sense and hopefully someone will be able to tell me the best solution for this scenario ?? Thanks in Advance.

Different Domains sharing an exchange organization is still possible, the easiest way to implement this is simply deploying a new domain tree / child domain in your forest & then deploying an exchange server in that domain. This also still maintains the central admin model since permissions from the forest root are propegated down to the domains beneath it.In my experience though most organizations that implement a root / child / tree domain structure eventually end up migrating away from it into a single domain infrastructure & then use multiple OU's for the management side of it. This proves much simpler in many respects.Consider installing your Factory server on your site, make it an additional domain controller & install it as an additional exchange server, allow for replication to take place then ship it to the factory for live environment. Use A/D sites to make sure clients authenticate at the correct domain controllers & routing groups to connect the exchange servers.Keep a seperate OU for factory which contains all their Servers, users, groups & computers & delegate the appropriate users / groups the admin rights to the exchange server & AD OU in the site.

So if I was to join the new server as a DC in my current domain, when you install Exchange on it do you get the option to join an existing organisation ? or do you have to set it up stand alone first and then create your routing groups ? I would have thought that you setup would see the existing Exchange Organisation. I recall exchange setup asking about joining a 5.5 organisation but haven't seen an option to join an existing exchange 2003 organisation. Given that the new server will be in the same domain will this option appear ?

Since A/D infrastructure came out in 2000 a limitation was put in place to allow only a single Exchange Organization to be deployed in a Forest, as such any exchange servers which you install after deploying the first exchange server & organization will automatically become a part of that org, there is no longer a need to specify which org to join.routing groups & administrative groups can either be created before or after the deployment of additional exchange servers depending on the requirements & preferences of the person doing the setup. there is no true advantage / disadvantage to either method if you initial deployment will be in the same location, the requirement would be that once it moves to the site location the routing groups & connectors should be configured & exchange server a member there of. Be aware that exchange needs to replicate this between itself as well as A/D for the changes to take effect properly so maybe allow it to sit for 12-24 hours with this config before shipping it off.also remember to run Domain Prep from the new exchange server before deploying to make sure all the security group memberships & domain rights are properly setup for the server object in AD.

So given that our new link between sites is called "Metro Ethernet" and will be an extension to our LAN rather than a WAN do you think it's worth setting things up as though the 2 exchange servers were in the same building full stop ? They will be on the same subnet on our LAN (no routing at all) and it's a 10Mbit link. What do you think ?? Over 10Mbits will there be that much traffic really from domain / exchange replication etc ? or will it go completely un-noticed ? I'm leaning towards setting it up here in our office and just shipping it over after a few days of smooth running.

If you have a 10mbps link & stretched subnet there would be no significant advantage gained from trying to seperate the sites / routing groups. In any case, site membership in AD is decided according to ip subnet on which the client / server resides so in your scenario this would look to the servers/clients as a single site. My experience says that 10mbps would not be significantly affected by AD/Exchange replication & data transfer unless you were running a network of over 10 000+ objects which all changed on a regular daily basis, and even in this case its doubtful you would see much of a load. Go for it! See how it works & if need be, just update your config when the time comes... Its really not a complicated procedure & will not generally result in down time either.

Many thanks Johan, I have a clear idea of which way to go now. Thanks again.