Tricky Exchange 2003 to 2007 Migration Path

We are going to be migrating to Exchange 2007 in the next month or so.

We have an existing 2000 AD with Exchange 2003 in it.

We have a new 2003 R2 AD that will have Exchange 2007.

My question is... with about 300 desktops and 35 servers in the 2000 AD which route would be better:

A)Installing 2007 into the 2000 AD, thus same forest, same org, makes moving mailboxes a bit easier, then once everybody/everything is migrated over, then either renaming the 2000 AD (obviously by getting some 2003 DCs in and demoting the 2000 DCs) to the 2003 R2s domain name


B)Keeping the new 2003 R2 domain, and doing cross-forest moves (which I understand is only possible via Exchange Command Shell currently) I imagine this is the cleaner route, but I'm a little hesitant about the possible gotchas/hiccups that may surface via this route.

Which solution would you recommend, and why? Does anyone have any experience with either scenario?
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czcdctConnect With a Mentor Commented:
Well, you can't actually do (A) since you need 2003 SP1 so your option there would be to upgrade the DCs in the 2000 forest, make it native mode (both AD & Exchage) and then introduce the 2007 into it.

But why are you asking this question? Haven't you made the decision to implement a new forest already, otherwise why else do you have the 2003 R2 based forest up and running?
Stacy SpearPresident/Principal ConsultantCommented:
I would do A. Having just finished a massive forest migration that was forced from higher ups, migrate only if necessary.

Bring in the 2003 DCs into A.
Demote the 2000 DCs.
Go native mode.
Bring in 2007.
Move the users in stages over to it.
After all users are over, verify that you've checked all the boxes and start decommissioning E2K3 boxes.
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ATIGConnect With a Mentor Commented:
The easiest thing for you to do is update your AD, it will funtion better with 2003 vs 2000 with improvements in replciation etc....

Once that is the case then all you need to do is a move mailbox.

Note you would need to install new CAS server first  if you use OWA or any other remote access users can go through the 2007 server to get to a 2003 mbx

make sure you have read up on 2007 as many thing are quite different from 2003

amedexittAuthor Commented:
Oh, there's a fly in the ointment.. we are still using the Instant Messaging from our Exchange 2000 Server that will eventually be replaced with Live Communications Server 2007.

Darkstar3d-What about renaming the domain after everything is said and done.

If the cross-forest migration weren't such a pain, I'd already be 100 percent behind B :)
ewww you did not even mention you had Exchange 2000 you only stated 2003 :P

czcdctConnect With a Mentor Commented:
There will be no renaming of the domain, that can only end badly for you. It might be supported in certain situations but I would most certainly avoid trying unless you're a six figure earning AD guru.
amedexittAuthor Commented:
Yeah, that exchange 2000 is like a red headed stepchild... :D It will have to be the cross-forest migration... but here's the one thing I can't get my head around:

When we migrated from NT4 to 2000, we used the ADC (Active Directory Connector) between the domains, and it worked well for transferring the mailboxes from Exchange 5.5 to 2000;

My question is, can one do the following: Move the User's mailbox to the new domain, but while we are still prepping, allow them to access it from BOTH domains; I remember we had done that for a few months where the user's NT and 2000 User Accounts (same username) had permissions to the mailbox to be able to open it from the either domain.
amedexittAuthor Commented:

I've actually seen that article before; Since I'm going to be doing 80 percent of this migration, I just wanted to make sure that we can migrate the mailboxes over and then associate them with the old domain as well, which it looks like we can do.

Do you (or anyone) have any tips that may help with doing this migration?
Stacy SpearConnect With a Mentor President/Principal ConsultantCommented:
ADMT, as stated, domain rename is not a good option. Exchange 2000 is a fly in the ointment as well.
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