Question : Exchange 2010 migration project from Exchanger 2003.

Current enviroment: Single Exchange 2003 Enterprise server.  Users use OWA and Outlook 2007 client.

Looking to migrate to Exchange 2010 enviroment with 2 CAS/HT and DAG with 2 MB Servers.  However NOT all at once. I want to deploy 2010 and move about 10 users over and have them try it out.

Question:  At what point will mail flow be "cut over" to the new CAS/HT servers?  How much "limbo" time am I looking at?  Can I please get a high level outline of 5-10 points with regards to what I need to do with DNS records both internally and externally?  One request: please do not answer with a link unless its very specific.

Answer : Exchange 2010 migration project from Exchanger 2003.

There are no DNS changes required.  All that's needed to change the mailflow is redirect port 25 so it is no longer going to the 2003 server but is going to the 2010 server instead.

Either way the Exchange organisation will deal with the appropriate delivery.  A few things to checkout when you do swap it over.  By default the Exchange 2010 receive connector doesn't allow anonnymous connections you will need to set this otherwise mail will be rejected.

Another common issue is a smarthost configured on the default SMTP Virtual server on the 2003 server.  Check out my article here: http://www.experts-exchange.com/articles/Software/Server_Software/Email_Servers/Exchange/Exchange-Server-Mail-Flow.html

I also have a migration guide here: http://www.experts-exchange.com/articles/Software/Server_Software/Email_Servers/Exchange/Migrate-Small-Business-Server-2003-to-Exchange-2010-and-Windows-2008-R2.html it's written for SVS2003 but the exchange and Active Directory parts are exactly the same.

And finally if you plan to use DAG make sure you are using Enterprise edition of Windows Server (you don't need Exchange Enterprise).  I have also written a DAG guide here: http://www.experts-exchange.com/articles/Software/Server_Software/Email_Servers/Exchange/High-Availability-Exchange-2010.html

there are a few links but they are my articles and I think quite specific :)