How can one migrate Exchange data to a new domain without joining the old?

There are a great number of very well written guides, just on this site alone, pertaining to the correct process by which to migrate information within Microsoft Exchange from one server to another.  The process (briefly) involves joining a later model server to the domain of the earlier server, adding exchange, migrating it, and decommissioning the old server.

That's all well and good, but as a network administrator of a small business with no more than 25 employees, I've really had enough of the old domain I inherited.  It wasn't configured properly and it isn't to my liking.  So I'm wondering if there's a relatively painless method by which I can get all my users email (because that is ALL they use this server for...until I show them otherwise) without actually joining this lovely new server to the icky old one.

Given the option I'd just export PSTs and reimport them into newly made user accounts, but several users don't understand the concept of archiving.  I believe one user has a mailbox that is over 13 gigs in size.

They're fairly concerned about things that might get left behind due to compliance/auditing reasons, but I plan to seal the old server for archiving purposes, and export all the mail on it to EML as well. (No, that's not my idea, but it should ensure we get nearly everything.)

So, suggestions? And yes, I suppose suggesting "What you're trying to do is a horrible idea." is also a valid suggestion.  (Provided you explain why, of course.)

Thank you in advance, regardless.  I tried searching for this, but all searches just turned up HOW to migrate exchange after joining to the domain rather than how to AVOID joining the domain to get the data across.
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As you said, your project is not usual.
You don't give any version exchange server version that you have and that you want to go...
It's an important thing to known because tools used to migrate can be very different depending version..
Let's assume :
-  old domain = Windows 2003 + Exchange 2003 -
- the new domain will be Windows 2008 R2 + Exchang 2010 SP1.
- you want only "migrate" mailbox data (for 25 mailbox) , no 'public folder' data,
A scenario that I can imagine:
1-  you will create a new AD forest with the new Windows 2008 R2 server as a DC
2- you will install a new Exchange 2010 Sp1 from scratch within  the new forest/domain
3- you will recreate from scratch users and groups, empty mailboxes and distribution list on the new system
4- you can export all mailbox data form exchange with the EXMERGE tool (free tool from Microsoft): it copies all data from multiple mailbox in PST files (creating one PST file for each mailbox)
5- you move PST File to the new server via network or usb HDD
6- you reimport data from PST Files in the new server. To do this: unfortunaly, EXMERGE cannot be used against Exchange 2010 Sp1 to restore PST in mailbox (not compatible with exchange 2007/2010 family), but
Exchange 2010 SP1 has a new feature with the same fonctionnality: the "Import-Mailbox" powershell cmdlet (only with Exchange 2010 Sp1)
7 you achieve migration with manually recreating other settings (SMTP internet mail flow, OWA access and config, etc...) based on the old server's settings

I think it is not very complicated but you simply need a long time to do this.  

PS: PST file cannot support 13 Gb in size in one file ! It is recommended to not go behond 2/4 Gb max for one PST file. If you have one Mailbox with a size of 13 Gb , you'ill had to split it into multiples PST files (manually, EXMERGE can't do it for you)
FoxKeeganAuthor Commented:
Oops, you're right. I didn't say version numbers, but you are spot on: 2k3 Server and Exchange, 2k8 R2 Server & 2010 Exchange.

I have a script designed to export mailboxes to PST with Exmerge, and it splits off to a new file when it hits the 2GB limit.  I've used it with success.

What you've described is the only method I know to do this manually, but I didn't mention it as I wasn't sure it was a complete solution. (And I'd not heard of the Import-Mailbox utility)

If all that method doesn't leave anything behind, I'm willing to go that route.  That should keep any lingering settings I haven't found in this domain away from the new one.

One issue: There is a single public calendar in a shared folder.  Will that be difficult to move to 2010?
Sigurdur HaraldssonSystem AdministratorCommented:
You're looking for the Remote Move Request:
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FoxKeeganAuthor Commented:
The Remote Move Request certainly looks like it'll handle everything in one fell swoop.  Thanks!
FoxKeeganAuthor Commented:
"While performing remote mailbox moves, the Microsoft Exchange Mailbox Replication service (MRS) uses the msExchMailboxGUID attribute to find matching users, thereby maintaining the Send As and Receive As permissions. MRS then maps the trustee to the matching user in the destination forest."

I'm trying to determine if the Remote Move Request works by simply taking an existing old mailbox, and asking you the username of the new mailbox, or if it requires the Mailbox GUID to be the same, as Exchange likes to do. If that's the case, it's not as useful as I'll have to join them in AD to copy over the users.
FoxKeeganAuthor Commented:
After a bit more research it seems as though both will work.  I don't have the equipment yet here to test this, but I'm pretty confident both methods will work.  (And I'll have everything backed up if they don't)

The following link aids in preparing something for such a shift as well:

It may be helpful to anyone who is about to attempt that which I plan.

Thank you both!
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