Now I know there are articles out there, but I wanted to write one that had enough detail for anyone attempting this to follow, but with as few steps as possible.
Obviously make sure you Exchange 2003 server is working well before moving to 2010.
- Check Default SMTP Virtual Server to ensure you do not have any smarthosts in there on the Exchange 2003 server (Under First Administrative Group – Servers – Servername – Protocols – SMTP). This will prevent mailflow between 2003 and 2010 servers.
- Install Exchange 2010 on the new server (I’m assuming single server here – not recommended by Microsoft). Plenty of articles on how to do this.
- Disable Linkstate on Exchange 2003 and reboot (or restart Exchange 2003 services) (Command Prompt to x:ExchSvrBin and type Regsvr32 -u xlsasink.dll)
- Move/create a mailbox onto the 2010 server. Connect Outlook or log into webmail on that server to conduct some tests. Test the following: Email flow between 2003 and 2010 mailboxes (both directions) and email flow from 2003 -> external and 2010 -> external
- If there are issues with mailflow between 2003 and 2010 delete and recreate the connectors. The connectors are setup automatically when you installed Exchange 2010.
- Replicate Public Folders and other instructions as per article (do everything but decommision the Exchange 2003 server): http://support.microsoft.com/default.aspx?kbid=822931
Do not change Replication Schedule or Replication Priority when replicating the Public Folders. You could end up bogging down the connectors with excess traffic and grinding the Exchange servers to a halt.
- Move mailboxes. You will have to do this with the Exchange 2010 ESM (not the 2003).
- For seamless transition with Outlook 2003 clients, you need to disable the requirement for encrypted connection.
Run this in the Exchange Powershell on the 2010 server:
Set-RpcClientAccess –Server <servername> –EncryptionRequired $False
Otherwise in Outlook 2003, you will need to choose the Encrypt Connection between Outlook and Exchange server option. This is not hard, however in migration scenerios, it will prevent seamless handover between legacy Exchange 2003 servers and Exchange 2010 servers when you are moving mailboxes.
- I would leave the Exchange 2003 server running for 2 weeks before removing to ensure there is a automatic handoff to the new Exchange 2010 servers when users connect in with Outlook for the first time. Otherwise you will be running around reconfiguring Outlook to point to the new 2010 server
- Rehome Receipient Update Services. Use the Exchange 2003 System Manager to do so. Point it to the other Exchange Server, and the correct Domain Controller.
- Remove Exchange 2003 server as per article above from Microsoft.
- It’s not unusual that during a process/migration like this to have errors with the Offline Address Book to Global Address List. If you are getting such errors during Sending/Receiving in Outlook, you may have to rebuild/recreate the Offline Address Book after all the above steps have been completed. Symptoms of a faulty OAB/GAL are that newly created users do not appear. A temporary workaround is to get your users to type in their full email address for the time being.