Transition From Exchange 2003 To 2010, Part 1…

As many organizations are thinking of skipping Exchange 2007 & moving directly to Exchange 2010 from 2003, I thought it is a good time to go through the process. The entire topic will be covered through multi part posts. I will base the entire series on my environment. Details of my network is listed below.

  • Domain HEW.LOCAL (How Exchange Works)
  • Domain Controller – 2003DC, running Windows 2003 R2 SP2
  • Exch 2003 Back End – 2003BE, Exchange 2003 SP2 running on Windows 2003 R2 SP2
  • Exch 2003 Front End – 2003FE, Exchange 2003 SP2 running on Windows 2003 R2 SP2
  • Exch 2010 CAS&HUB; – CASHUB, Exchange 2010 running on Windows 2008 R2
  • Exch 2010 Mailbox – 2010MBX, Exchange 2010 running on Windows 2008 R2
  • 2003 OWA URL –
  • 2010 OWA URL –

In this post, we will discuss the requirements for Exchange 2010 to coexist with 2003 in the same active directory domain. I already have a 2003 domain up and running with Exchange 2003 Front/Back End configuration. I have also installed two member servers with 2008 R2 (CASHUB & 2010MBX). Before we introduce an Exchange 2010 server, the following points have to be checked.

1. The AD forest & domain functional level has to be atleast Windows 2003. Launch AD Domains & Trust, select the domain name, right click & select properties. Make sure the forest & domain functional level reads “Windows 2003” or higher. In my environment, I have both functional level at Windows 2003.

Fn Levels

If the functional level is below Windows 2003, raise both forest & domain functional level using the same interface. Right click “AD Domains & Trust” and select “Raise Forest Functional Level” & raise it to Windows 2003 or higher.

Raise Forest Fn level

To raise domain functional level, right click the domain name and select “Raise Domain Functional Level” & raise it to Windows 2003 or higher.

Raise Domain Fn Level

2. The Global Catalog and Schema Master should be running atleast Windows 2003 SP1 or 2003 R2.

3. The Exchange 2003 Organization should be running in “Native Mode”. To check, launch System Manager & right click the root (Exchange Org name) and select properties. By default, it will be in mixed mode. Click the “change mode” button to change it to native. It is a one way process.

Change Exch 2003 Mode

4. Disable link state updates on all Exchange 2003 servers (to make sure that routing loops won’t occur) with a registry edit. Exchange 2010 doesn’t use a link state routing table and don’t support relaying of link state information. If you don’t suppress minor link state updates, routing loops may occur. Follow the technet article for the registry edit. The first routing group connector is created when the first 2010 Hub server role is installed in the Exchange 2003 organization. The registry edit forces earlier versions of Exchange to use least cost routing and not to calculate an alternative route.

As a final step, use the Exchange 2010 Pre-Deployment Analyzer to make sure that your environment is ready to have an Exchange 2010 deployment.

In the next part, I will discuss the pre-requisites for Exchange 2010 & installation steps for introducing your first 2010 server to the 2003 organisation. Stay tuned!

14 thoughts on “Transition From Exchange 2003 To 2010, Part 1…”

  1. Hi,

    Thanks for your really help full post. where is the part two.

    I will be doing transition from 2003 to 2010 currently we are using https:\\\exchange . can i use same for 2010 and put https:\\webmail.domianname\owa instead, will it work.

    plaease let me know where i can find part two.


  2. Hi,

    You can use the CAS array name the same one as webmail. You can use an internal name as well like outlook.domain.local. There is no hard and fast rule. Your web services should have webmail, as that will be the one covered in the certificate and will be accesses from outside as well, example autodiscover.

  3. hi rajith,
    thanks for the answer. i will use a new name for Exchange 2010 OWA.

    just a bit confused with putting them all together. so i use as the external URL for the internal facing CAS which i specified during the installation.

    I also have CAS array FQDN
    I don't want to use as cas array FQDN as I don't think this is a good practice.
    so in my case, which do i use when setting up autodiscovery, OAB, etc? or

    or should i just use the same name to avoid confusion?

  4. hi,
    do you find any problem at all using a new name for Exchange 2010 OWA (, and keeping the existing name for Exchange 2003?
    Will that raise any issue in the future for not using instead?


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