Preparing for 2003/2010 coexistence, isn't this the least impacting way for upgrading the OAB ? Create new OAB on 2010 (not a move) with the web distribution points on your CAS hosts. Associate the new Exchange 2010 mailbox databases with the new OAB. Keep the default 2003 OAB on the Exchange 2003 server until the mailbox migration is done.

Sure...this is absolutely a valid approach. Not sure what version of Outlook you are running, if 2003 then you will also need to distribute the OAB via public folders. Your way will definitely work.Tim Harrington - Catapult Systems - http://HowDoUC.blogspot.com

Personally I always retain the OAB on Exchange 2003 and setup public and system folder replication. The Exchange 2010 servers are setup for both web and public folder distribution. The OAB changes are then part of the procedure for the removal of Exchange 2003 server. I am looking to keep changes to a minimum, and if the Exchange 2003 server is generating the OAB for all users correctly, then it should be left to get on with it. There is very little to be gained having multiple OABs. Simon.Simon Butler, Exchange MVP. http://blog.sembee.co.uk , http://exbpa.com/

I've had trouble where the old OAB simply wouldn't work and I had to create a new one. It's no big deal to do that. -- Ed Crowley MVP "There are seldom good technological solutions to behavioral problems." . "Sembee" wrote in message news:27f621f0-82c8-4507-b8c7-53097dad6b73... Personally I always retain the OAB on Exchange 2003 and setup public and system folder replication. The Exchange 2010 servers are setup for both web and public folder distribution. The OAB changes are then part of the procedure for the removal of Exchange 2003 server. I am looking to keep changes to a minimum, and if the Exchange 2003 server is generating the OAB for all users correctly, then it should be left to get on with it. There is very little to be gained having multiple OABs. Simon. Simon Butler, Exchange MVP. http://blog.sembee.co.uk , http://exbpa.com/Ed Crowley MVP "There are seldom good technological solutions to behavioral problems."

Hi, In order to ensure full functionality with Exchange 2010 features, we recommend that you move the OAB generation to an Exchange 2010 mailbox server. Moving the OAB generation will result in a full OAB download for all clients. You can generate the OAB from an Exchange 2003 server provided that public folder distribution is enabled. However, if you generate the OAB from an Exchange 2003 server, you will lose the following functionality: Japanese phonetic display name Japanese phonetic surname Japanese phonetic given name Japanese phonetic company name Japanese phonetic department name PR_DISPLAY_TYPE_EX, which is used by Office Outlook 2007 and later to render the correct icon for objects that are replicated across the forest. More information: Exchange 2010 Deployment Assistant http://technet.microsoft.com/en-us/exdeploy2010/default.aspx Move the Offline Address Book Generation Process to Another Server http://technet.microsoft.com/en-us/library/bb125184.aspx Thanks, Elvis

Hi, In order to ensure full functionality with Exchange 2010 features, we recommend that you move the OAB generation to an Exchange 2010 mailbox server. Moving the OAB generation will result in a full OAB download for all clients. You can generate the OAB from an Exchange 2003 server provided that public folder distribution is enabled. However, if you generate the OAB from an Exchange 2003 server, you will lose the following functionality: Japanese phonetic display name Japanese phonetic surname Japanese phonetic given name Japanese phonetic company name Japanese phonetic department name PR_DISPLAY_TYPE_EX, which is used by Office Outlook 2007 and later to render the correct icon for objects that are replicated across the forest. More information: Exchange 2010 Deployment Assistant http://technet.microsoft.com/en-us/exdeploy2010/default.aspx Move the Offline Address Book Generation Process to Another Server http://technet.microsoft.com/en-us/library/bb125184.aspx Thanks, Elvis

John, Have you considered not coexisting? If you migrate everyone to the new exchange environment at once (or relatively so), then there is no need for the complexities of coexistence. Without knowing your full scope, i can still say that only in rare cases is coexistence actually and technically required. I say this as CTO of Priasoft - i'm in charge of design and architecture of our migration solutions. We can show a migration design, even up to 2TB, that can migrate everyone in less than 48 hours. you can contact me if you like at eriq.vanbibber@priasoft.com -Eriq