Exchange 2010 Coexistence with 2003 - New install

Posted on 2011-03-03
Last Modified: 2012-05-11
Hi experts,

First time using this resource so forgive me if I don’t know all the procedures.

I am installing Exchange 2010 in a 2003 environment, below is my 2003 server environment.  
•“Email” – Clustered mailbox servers
•“OWA” – Client access
•“Exchange” – Public folders

•“Email01” - First 2010 CAS

I have done all the pre-prep work already (legacy, schema, AD prep), and started the installation of the first 2010 HUB/CAS server, I want to coexist the two environments for testing and later staged user migration (due to our size). I am at the part of when asked if this CAS will be internet facing, enter domain name … is this my “” or our external URL “

Second, I am trying to understand the part about using legacy host name, and the coexistence of the two environments.  My goal is to make sure external and internal user are not interrupted to how they access their email whether they are on 2003 or 2010 during the setup and testing.

I am reading the part about how to “Configuring CAS” and setup legacy name, my question is that the steps in this article say to run these commands
•Enable-OutlookAnywhere -Server:<CAS2010> -SSLOffloading $false
•Set-OABVirtualDirectory <CAS2010>\OAB* -ExternalUrl
•Set-OwaVirtualDirectory <CAS2010>\OWA*  -Exchange2003Url
And so on.....

From what I understand is that I am using the same URL and hostname as in 2003, my concern is at any point in time well doing these changes will a user get redirected to 2010 and not see his mailbox because his mailbox still lives on 2003?

Question by:lake_user
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LVL 74

Accepted Solution

Glen Knight earned 250 total points
ID: 35030471
OK, basically you need to create the legacyURL and the regular URL.

So that users don't get interrupted use the existing URL to point to Exchange 2010 CAS server.
Then the legacyURL setup something like, Outlook 2010 will automatically re-direct users to the legacy mailbox if they exist on the 2003 server.

So as long as you have the legacyURL and the setting in Exchange configured BEFORE you make any firewall changes you should be OK.

Expert Comment

ID: 35030497
They should not be affected because you will be creating a legancy external dns name; which the IP will be pointing to your 2003 owa server IP.  You will have the same internal dns name as well too.

Author Comment

ID: 35030752
Thank you both for the quick response.

What about other vers of outlook?

And can either one recommed a good step-by-step reading on this?    
LVL 74

Expert Comment

by:Glen Knight
ID: 35030788
Which version of Outlook are you refering to and what do you want to do with them?
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Author Comment

ID: 35030856
Well, you stated that Outlook 2010 will automatically re-direct users to the legacy mailbox if they exist on the 2003 server. What about user on Outlook 2002, 2003, 2007, and Mac 2004 & 2008? I believe Exchange 2010 does not support 2002?
LVL 74

Expert Comment

by:Glen Knight
ID: 35030883
Sorry, that was a typo, it should say Exchange 2010 not Outlook 2010.

Exchange 2010 does support Outlook 2002 but you will have to disable rpc encryption on the Exchange Servers as it's not suported in Outlook 2002.

Outlook will automatically detect the new CAS/Mailbox server for the appropriate users so you don't need to worry about that.

Author Comment

ID: 35030956
That's what i thought you may have meant but i wanted to make sure. What about a good step-by-step doc (or link) on configuring the CAS and legacy setup?
LVL 74

Assisted Solution

by:Glen Knight
Glen Knight earned 250 total points
ID: 35030975
There is a full co-existence guide here:
I am not aware of any others that specifically cover the CAS and legacy setup step by step.
LVL 74

Expert Comment

by:Glen Knight
ID: 35356780
This question has been classified as abandoned and is being closed as part of the Cleanup Program. See my comment at the end of the question for more details.

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