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Migrating from Exchange 2003 to Exchange 2010 - Client Access Server Role

We are in the process of migrating from Exchange 2003 (SBS) to Exchange 2010..  We are currently running BES 4 Express and Activesync for iPhones.  The plan is to install BES 5 on the Exchange 2010 server after it is installed and migrate users over, since there's no direct upgrade bath from BES 4 Express to BES 5 Express.

OWA is externally accessible from https://mail.mycompany.com/exchange.  
Sharepoint/Remote Web Worplace is accessible on the same server from https://mail.mycompany.com/remote

If make the Exchange 2010 CAS external domain the same https://mail.mycompany.com, it will break Sharepoint, since it's on the same server.   It will also break Activesync for current users as well?   I'm assuming BES continues to work though?

Can I do the following?

Keep https://mail.mycompany.com for the current server
Make the CAS external domain https://mail2.mycompany.com and externally accessible.

As we move users over to the Exchange 2010 server, we will have them re-configure their iPhones and Outlook to go to https://mail2.mycompany.com.  I'm assumingwe'll have to create a new profile in Outlook, and that it won't just migrate them over.  And, if they have a BlackBerry, we will re-activate them on the BES 5 server after we move them.

Will this option work?


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Justin Durrant
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You should use 2 external domain names, in the official microsoft documentation the assign legacy.yourdomain.com to the exchange 2003 and mail.yourdomain.com to the exchange 2010, but you can use all kind of names you like.

If you move mailboxes from one server to the other outlook would recognize this and will automatically change the configuration, this is also for iphones so you don't have to do this manually.

Make sure you have done your preparation correctly read the migration documentation: here is a good start: http://technet.microsoft.com/en-us/library/dd638130.aspx

If you are migrating the complete sbs 2003 away this is a great manual http://demazter.wordpress.com/2010/04/29/migrate-small-business-server-2003-to-exchange-2010-and-windows-2008-r2/
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The question is, if I use 2 external domain names / name spaces, does each Exchange server operate independently?  Will Activesync function on both servers separately?  Say a user1 is on mail.mycompany.com and user2 is on mail2.mycompany.com, will Activesync work on the separate addresses, or does Exchange 2010 take over anything?
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Justin Durrant
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Exchange is the server side of a collaborative application product that is part of the Microsoft Server infrastructure. Exchange's major features include email, calendaring, contacts and tasks, support for mobile and web-based access to information, and support for data storage.

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