Joining an exchange 2003 server to an Exchange 5.5 Org.

We manage one site in a global exchange organization. The rest of the Org are going to create an AD forest but not for a ages and they're not expecting to upgrade exchange for years. However we are already running our own seperate AD Forest and want to install Exchange 2003.

Currently or 5.5 server connects to a 5.5 remote bridgehead server via x400. We propose a staged migration to exchange 2003 using ADC to sync the 5.5 database with AD and replicate Public folders, whilst sending mail and replicating Gal changes via x400. Eventually we hope to decom the old 5.5 server and run with exchange 2003 only.

We've tried out this configuration in our test environment but I'm a little concerned about the implication of being the first 2003 server in the Org especially with respect to the ADC agreements being 'Primary' connections.

I'm worried that changes we make will impact the rest of the org...
can anyone see any problems with this set up?
Will being the first AD forest to join the Org cause problems when the rest of the Org decide to implement there own AD Forest?
Will ADC/exchange 2003 try and make changes to the other exchange sites and servers?

Any help with this would be really appreciated.

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munichpostmanConnect With a Mentor Commented:
I will try and answer this.

Will being the first AD forest to join the Org cause problems when the rest of the Org decide to implement there own AD Forest?

You can only have one Exchange 2003 organisation in a forest. You are already running your own AD Forest. You would need to run forestprep to prepare the forest for Exchange 2003 followed by domainprep. If the rest of your organisation wishes to upgrade to Exchange 2003 and want it running in a seperate forest at some point in the future then you should not run forestprep and install Exchange 2003.

You will have to install a clean Exchange Organisation into your AD Forest and look at migrating user accounts and mailboxes into the seperate forest.

Will ADC/exchange 2003 try and make changes to the other exchange sites and servers?

This can be controlled, however the key thing is that if the rest of the Exchange Sites in your Exchange Organisation will have Exchange 2003 servers installed from a separate forest, then you should not install Exchange from your AD forest.

Here is some more background info on Forestprep and domain prep

To answer your question more clearly (English is not my first language)


There is one Exchange 5.5 organisation with four sites. You manage one of those sites, your organisation the rest.

You have an AD Forest, your organisation will create one at some point in the future and will upgrade to Exchange 2003 at a later date.

Before you can install Exchange 2003 you must run Forest prep in the AD forest in order to extend the schema with Exchange 2003 attributes. During the forestprep setup, it will ask if you wish to join an Exchange organisation or create a new one. If you join the exsisting Exchange 5.5 organisation, the rest of your organisation will also have to use your AD Forest if they wish to maintain the functionality they currently have in Exchange when they upgrade to Exchange 2003.

You should consider creating a neutral central forest and installinge Exchange 2003 there. Migrate user accounts across to the new forest. The rest of your organisation could also migrate to the neutral forest. There are a number of tools which enable you to do this such as QWEST Migrator,
thomalskiAuthor Commented:
Thanks for your prompt response.

I know that an Exchange 2003 org can only exist in one Forest but does that really apply for 5.5 orgs too?

I thought that i could join the ex2k3 to the ex5.5 org and other AD forests could join the Ex5.5 org asclong as it wasn't native ex2003?

What do you mean by other AD Forests can join the org? You can only install Exchange 2k3 from one AD forest into an Exchange 5.5 organisation.
thomalskiAuthor Commented:
Thanks again.

The nature of our business means that we have implemented our own AD forest whilst the rest of the comapny (worldwide) intend to deploy a sepearate Forest. It will probably remain a mixed mode Exchange org for many years to come.

I was hoping it was possible to have two AD forest in this mixed mode exchange 2003/5.5 org. If this is just no possible then I'll close the call once you respond.

Thanks again for you help.

We currently connect our site to the rest of the organisation using an x400 connection. There are notes servers in the org too so perhaps we could join our current exchange 5.5 server to a notes bridgehead, remain part of the org and keep our sepearate forest. Will post this as another question. ;0) Thanks again, you've been a great help!
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