I have seen a lot of questions on what will happen to Outlook profiles when you migrate a user to Exchange 2007. First, let me say, that in order for you to migrate to Exchange 2007, you have to upgrade your previous version of Exchange (2000 or 2003) to the latest service pack. That is part of the puzzle as the latest service pack enables the functionality for an Outlook client to automatically updates its’ profile.
So, let’s take a look at the release notes for Exchange 2003 SP2 which you can find here. The part we are interested in is:
Changes to how DSProxy Referral Mechanism Works
In Exchange Server 2003 SP2, the DSProxy referral process now tries to provide an Outlook client that has a global catalog that belongs to the same domain as the mailbox-enabled user by using a new algorithm. The new algorithm examines all global catalog servers that are directly connected to the Exchange server Active Directory site and provides the client with a global catalog that resides in the same domain as the mail recipient, if possible. This means that Exchange can now refer clients to out-of-site global catalog servers if there are no mailbox home domain global catalogs available in the Exchange server Active Directory site. For detailed information about DSProxy in SP2, see Microsoft Exchange Server 2003 Technical Reference Guide.
Now prior to Exchange 2003 SP2, if a client’s profile got moved to another Exchange Server, as long as it was in the same Administrative Group, DSProxy would automatically refer the Outlook client to the other Exchange server. The Outlook client would then update its’ profile. Now in SP2, DSProxy was changed so it can refer users to an Exchange server in a different Administrative Group. This is essential since Exchange 2007 gets installed into its’ own dedicated Administrative Group where all Exchange 2007 servers live. This Administrative Group is called FYDIBOHF23SPDLT.
So what had to happen prior to Exchange 2003 SP2 to allow you to move a client across an Administrative Group? You would use a tool called The Exchange Profile Update Tool (ExProfRe). This tool can be run in a logon script, group policy, or manually. You can download this tool from here. And a tip. The documentation for ExProfRe is in the self-extracting .EXE so don’t go searching Google for hours trying to find the commands to use for ExProfRe.
Now let’s say you’re migrating to Exchange 2007. Typically, after the last user has been migrated, you want to leave your Exchange 2003 Back End Servers that hosted mailboxes up for a period of time to ensure you have provided your users enough time to be referred automatically. For the stragglers (people on vacation, out on maternity leave, etc.), you can either manually update their profile or use ExProfRe to get their Outlook profiles updated. What I typically do or at least recommend is to leave your Back End up for a week or two and then shut it down for a few days to ensure no unknown dependencies were missed. You can then bring it back up if all goes well and decomission it.
Another option is to update their profile with a PRF file. For Outlook 2003, you can create a custom PRF file using the Custom Installation Wizard. This PRF file allows you to create a new profile or manage existing profiles. For more information on how to do this for Outlook 2003, go here. For Outlook 2007, the procedure is the same as Outlook 2003 except you use the Office Customization Toolkit instead. For more information on how to do this for Outlook 2007, go here. There are scripts out there that you can run via login scripts that allow clients to apply a PRF file once (sets a registry key when run) and the next time it runs it checks for a registry key and halts PRF execution.
I feel that in the situation that you want your client to only be re-directed to another server due to the source server having been decommissioned, ExProfRe would be the fastest and easiest method to accomplishing what you need.