How-to configure Coexistence between 2003 and 2010

[Andersson]

Hi

 

After reading and answering in MS forum I can tell you all that this is a very common question that need to be clarified.

 

Before Exchange 2010 was released there was a built-in function that handled the co-existence for OWA.

A little background check, Exchange 2003 and 2007 could co-existence by pointing to the Exchange 2007 CAS server(s) and use /exchange.

 

In Exchange 2010 this function is removed and replaced by “Legacy”.

 

What to think about when you are planning for a co-existence?

 

1. You need to add the legacy.domain.com name to the certificate that will be used on the CAS server(s).
2. Change the external URL on Exchange 2007 (OWA) by using EMC or EMS.
   http://technet.microsoft.com/en-us/library/bb123515(EXCHG.80).aspx Set-OwaVirtualDirectory -ExternalUrl ‘https://legacy.domain.com/owa’ -Identity ‘CASSERVER\owa (Default Web Site)’
   
   If Exchange 2003 is used with co-existence you have to do this from Exchange 2010 EMC or EMS from Server Configuration -> CAS -> Outlook Web App. Select Exchange 2003 and type in legacy.domain.com as the external name.
   Or using cmdlet;
   Set-OWAVirtualDirectory -Exchange2003URL ‘https://legacy.contoso.com/exchange’ -Identity ‘CASSERVER\OWA*’
   
3. Make sure that Windows Integrated is used on the OWA sites (NTLM) so it will be single sign on.
4. Add a DNS record for legacy.domain.com to point to Exchange 2003/2007 server.
5. Final step will be to change the firewall rules so it instead of pointing to the old server, point it to the Exchange 2010 CAS server(s).

I hope this will help someone!

 

If using this example in your organization, make sure to test it before using it.

No warranties, use at your own risk.

 

Also, here’s a helpful link from TechNet:

http://technet.microsoft.com/en-us/library/ee332348.aspx