Proposed project ahead, and a whole lot of documentation and options out there, so I was looking for opinions or advice.
I'm creating a brand new domain and installing Exchange 2010 in the environment. Server 2008 will be the DC. Is there a way to migrate existing mailboxes or entire mailstore to new domain, and then mapping those mailboxes to new user objects in the new domain (that will correlate to the old user objects….a manual process I'll be doing). Is this a smarter course of action, or should I use ExMerge to export/import the mail to empty mailboxes I create for the new user objects?
We don't want any of the ghosts of the old domain to come over, so creating from "scratch" is the intent. Obviously documenting, and then recreating, user objects, group membership, and permissions will be key. Just looking for some thoughts on how other users out there would attack this undertaking. There are arguments for maintaining the old setup for comparisons sake, and joining making the new DC part of the old domain, then doing a DOMAIN RENAME is intriguing, I hate being Wizard dependent and running into interrupted migrations and compatibility issues, leaving me dead in the water.
Best Answer
I can speak to how we handle our cross-forest mailbox migrations from our 2003 environment into our new 2010 environment. This process works reasonably well, except for a known issue that cross-forest mailboxes sometimes need a few hours to be recognized by Exchange 2010 (Or, you can restart the Information Store to get them up immediately)
Here's the process we use. There are alternate ways to make it happen, but this works for us in a production environment and we do this almost daily.
Prerequisites
Process
New-MoveRequest -RemoteLegacy -Identity "foo@contoso.com" -RemoteGlobalCatalog "GC.contoso.com" -TargetDeliveryDomain "New.Forest.Domain.Com" -RemoteCredential $foo -verbose
Where
Additional info
I would include the "expected" output of the New-MoveRequest verbose, but I don't have a mailbox to move at the moment to show. Suffice it to say, if you see lots of yellow spam without any red entries, things should be rocking and rolling just fine.
You can also check the status of the moverequest as it's processing by using
Get-MoveRequestStatistics -Identity username
Oh, an additional item: If when you attempt to use the new mailbox you get an "Unable to open message store", this is the "known issue" I referred to above. If you have a Database Access Group setup, we've found that failing over the DAG to a secondary server usually clears this up without an info store reset, though in some cases you need to cycle all of the info stores! Microsoft hopefully will fix this in SP2 (apparently wasn't important enough for SP1)
Good luck, and I hope this helps!