Moving Exchange 2003 to Exchange 2010

I am about to begin the process of moving Exchange 2003 to Exchange 2010. I understand that they will exist as separate servers but will work together. Can someone give a little more detail to this? How exactly do the work together during this transition? For example, if I enter a setting incorrectly or have to shutdown the server for maintenance for a day will it effect anything? Will the external access or OWA be affected?
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First you need to install Exchange 2010 in existing exchange organization. Once you installed Exchange 2010 successfully then need to move the database & other required setting from Exchange 2003 to 2010. Once you configured the all required changes on Exchange 2010 then shutdown the Exchange 2003 server for some days to check the dependency. If you not found any dependency on Exchange 2003 server & found everything ok then you can uninstalled exchange 2003 from exchange organization.

Use the attached file for transition from Exchange 2003 to Exchange 2010.

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Dav GrayIT ManagerCommented:

Firstly moving or migrating from Excgange 2003 to 2010 is a major task but can be easily achieved if done properly. I would suggest re-creating your environment virtually (VMWare, HyperV etc..,) to pre-empt problems that may arise as a result in moving to 2010.

Things to consider:

Ensure you have recent valid backup of your existing Exchange server including mailboxes and system state (AD, Schema master etc...)

Ensure you have completed all pre-reqs of Exchange 2010 before even running the set up exe.

Exchange 2010 will automatically upgrade your existing Active Directory Schema as part of the install process, once this is complete you cannot go back without risking corruption of the AD database.

Both Exchange 2003 and 2010 can co-exist on different servers. Exchange 2010 will automatically pickup the structure. You will notice when using Exchange 2010 console that there are a number of changes to its layout - read up on these.

Whilst in this co-existive state, Exchange 2003 is still your native version so any maintenance you intend to do on this server will affect the operation of email to users unless you migrate the mailboxes accross to the Exchange 2010 server.

You need to bear in mind that any email relate DNS entries made originally will need to be changed when you are ready to migrate for instance the Autodiscover service.

The OWA url will also need to be considered. If you have not already consider changing it to something like:

Here are some useful guides to digest and are very recommended.

Hope you will find my tips above useful.
Adam BrownSr Solutions ArchitectCommented:
Generally the way coexistence works is when a user connects to the 2010 CAS server and their mailbox is mounted on the 2003 server, they are forwarded to the Exchange 2003 server for access. Essentially the Exchange 2003 server will operate as normal, but the Exchange 2010 system will more or less coordinate and control the user interaction with the system. This is why you have to stand up (at a minimum) an Exchange 2010 CAS server before bringing a hub/mailbox server online (More often, though, you just bring up an entire Exchange 2010 server, since it's perfectly okay to have all three roles on one server).

The interaction between Exchange 2010 and 2003 is handled with a DNS record for the Exchange 2003 server. You move all your and DNS records to point to the new server (or just switch your port forwards) and the Exchange 2010 server will handle mail flow and user access, redirecting users to if their mailbox is on the 2003 server. If the 2003 server goes down for some reason, users with mailboxes on that server will no longer have access to their mailboxes and their incoming mail will stop, but users on the 2010 mailbox server will still have access and mail. If the 2010 server goes down, the same will happen to those users, but users on the 2003 server will still be able to access their mail from the URLs.
aandoAuthor Commented:

Just to be clear, until I make the changes to my DNS or port forwards, my new Exchange 2010 install will have no effect on my current Exchange 2003 server or mail flow?
Adam BrownSr Solutions ArchitectCommented:
Sorry. Yes, until you make port forwards to Exchange 2010, you'll see no difference in the way things work. However, if you move any mailboxes to the Exchange 2010 system, those users will only be able to access their mailbox through the Exchange 2010 CAS server. Exchange 2003 doesn't forward users to newer mail systems.
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