Can I upgrade Exchange 2003 to 2010 directly?


I know we can upgrade Exchange 2003 to 2010 directly in general, but not sure if it is still OK in my case.
My Windows 2003 AD domain controller and Exchange 2003 are in the same machine (called dc-exch). In theory, there are two options.
Option#1: Direct Exchange upgrade.
Step#1.1 Install Exchange 2010 on Windows 2008 (exch2010).
Step#1.2 Migrate all email functions from dc-exch to exch2010.
Step#1.3 Remove Exchange 2003 from dc-exch machine and turn it into a pure DC.

Option#2: First separate Exchange 2003 from DC, then upgrade.
Step#2.1: Install Exchange 2003 on Windows 2003 (exch2003).
Step#2.2: Migrate all email function from dc-exch to exch2003.
Step#2.3: Remove Exchange 2003 from dc-exch and turn it into pure DC.
Step#2.4 Install Exchange 2010 on Windows 2008 (exch2010).
Step#2.5 Migrate all email functions from exch2003 to exch2010.
Step#2.6 Retire Exchange 2003 server (exch2003).

Q#1. Is option#1 feasible?
Q#2. If yes, any precautions during the transition?


Who is Participating?
Scenario #1 will work and is supported. Been there, done that. :)

What you can't do is demote a DC with Exchange, but removing Exchange from a DC is allowable.
Yes option 1 is feasible. However, I would add a second 2008 DC first. then decommission the domain controller role from the 2003 box. Build a Exch 2010 box on 2008 and migrate the 2003 users over.

This will take care of AD 2008 first, then migrate to Exchange 2010.

You also want to take into consideration which client you are using. If you can, upgrade the client versions first also.
richtreeAuthor Commented:
I need to keep the Windows 2003 DC in order not to spend money on the license for Windows 2008 DC.
Any precautions for option#1?
Any lessons or tips from that experience?
Microsoft's has a deployment assistance here: - it just WORKED for me.
richtreeAuthor Commented:
Thank you.
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