Can we have 2 separate Exchange 2007 installations in one forest?

Win2k3 Forest, All servers are Win2k3

Parent Domain:

Child Domain 1:, child1DC

Child Domain 2:, child2DC


Can we have separate Exchange 2007 installations on Child1 and Child2? Reason for this is we are trying to merge 2 companies, but we want each one to have it's own Exchange and AD infrastructure.


Also, read a few posts that state you can have only one Exchange organization per forest.  What does this exactly mean and how will this affect the above?


Depending on how the above info is answered, I have this other issue. Exchange 2007 is up and running on child1 domain, but when trying to install on child2, I get this error when setup checks the 4 roles I want the server to handle:

Setup encountered a problem while validating the state of Active Directory: Failed to create a connection to any of the servers in the topology provider

netstat shows nothing is being blocked, and the DC seems to be running fine. Running DCdiag on the DC does not show any issues, and a search for this error does not return anything useful anywhere. Nothing is recorded in the event logs as to the cause of the problem. Any suggestions?
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You can have multiple exchange 2007 servers in 1 forest, provided that they are in the same exchange organization.  See this article:
parinpatelAuthor Commented:
That's not what we're looking for.  We're looking for 2 separate Exchange organizations in one forest.  An exchange organization is installed in and we're trying to install another exchange organization in
Sorry, I didn't read your post correctly.

Unfortunately that is not really each exchange organization requires a separate Global Catalog server in its own forest.  

This can only be done by creating a separate forest for the other exchange organization. Here is an article that describes cross forest authentication and how to set up exchange in this situation, as this would solve the issue.  

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parinpatelAuthor Commented:
Thanks, that's what I figured.

Couple more questions:

1. I know Exchange 2007 can exist in a root forest (as a resource).  Can we have 2 child domains in that forest named, and create users in each domain that have a mailbox in the root forest?  This arcticle ( states that you need a provisioning process between forests.  Now what I'm accomplishing isn't multiple forests, just one forest and 2 child domains.  

2. If I can do the above, how will it handle collisions or same names in each child domain or even at the forest level?  If I have 2 users, and how will I create an Exchange mailbox for each of these users in the root?  Will it handle the same name meaning will it filter down all the way to the domain and create a unique exchange mailbox by domain name?
parinpatelAuthor Commented:
Answering my questions based on my test environment I setup.

1.  Yes, you can have multiple child domains.  No provisioning needed, only needed if you are dealing with mulitple forests and want to have exchange in one forest and all of the users who need to access exchange in another forest.

2.  It will filter down and you will be able to choose which user you want create an exchange mailbox for.  Same names won't matter except only when it creates the default root email address entry for the user, it will append a "2" after the name if the same name already exists.  It doesn't matter in our case because we wil not have email addresses instead, we will create multiple recipient policies that will stamp users with certain custom attributes with a specific email address.
parinpatelAuthor Commented:
After more research and jasonwebb's answer, seems like what we were trying to do really is not possible, so we're going a differetn route to achieve what we need. Thanks!
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