I have an SBS 2003 bundled with Exchange 2003. I wanted to move the Exchange Server role to a Standard Windows Server 2003 and decommission the SBS 2003 afterwards. What are the steps I need to take to make this migration successful?

Normally you would be told to purchase the transition pack. However I don't believe that is available any longer. Therefore you are looking at a fresh purchase of OS and Exchange. You have a choice of either SBS 2008, SBS 2011 in the new year or Windows 2008 R2 and Exchange 2010 (with their relevant CALs). The only way you could use Exchange 2003 would be to purchase Exchange 2010, plus CALs and use downgrade rights. However that is like buying a brand new car just for the wheels and putting the rest in the garage to rot. With regards to doing the migration, there are many many different aspects, all of which are much too long to go in to here. Your best option may well be to engage a consultant, either Exchange or if you are going to migrate to SBS 2008/2011, a small business specialist. Simon.Simon Butler, Exchange MVP Blog | Exchange Resources

Done a few of these migrations and you basically will need to install an additional windows 2003 dc in your current SBS domain, seize FMSO roles move files, printers, shares, etc., then install Exchange 2003 and move mailboxes, public folders, etc. You then need to remove the first Exchange 2003 server by following http://support.microsoft.com/kb/822931. Then remove SBS 2003 Exchange from Add/Remove Progams and DCPROMO the SBS 2003 out of the domain. I would suggest setting up a test lab to go through this scenario as explained first then perform the migration but its actually pretty smooth.MVP Exchange Server

In reviewing some of my past migration notes, after joining additional DC in the SBS domain then make it a GC. You will only seize all FSMO roles when you have completed them migration ( right before you DCPROMO the SBS server out of the domain). I would also suggest running replmon after joining the windows 2003 dc to insure replication is successful between the DC's. I would also suggest running NETDIAG and DCDIAG at this point to insure everything is clean before starting the migration.MVP Exchange Server

John, When I get to the point where both servers are running Exchange Server 2003, and the moving of mailboxes is started, will there be problems receiving emails for mailboxes already moved to the new server since port 25 is still forwarded to the original server?

I started the migration today. The DCPROMO on the 2003 Standard server failed as it is running the R2 version. Is it safe to run adprep /forestprep and adprep /domainprep on the SBS server?