When target migrated users are accessing their source mailboxes the following error occurs in Outlook:
20:59:21 Synchronizer Version 11.0.6352
20:59:21 Synchronizing Mailbox 'oab issue'
20:59:21 Microsoft Exchange offline address book
Also, if the "Send/Receive" button is clicked then next error is displayed in "Errors" tab of "Outlook Send/Receive Progress" window:
"Task 'Microsoft Exchange Server' reported error (0x8004010F) : 'The operation failed. An object could not be found."
The issue is caused by the way Exchange store provides Offline Address Book to an Outllok client accessing it, see http://blogs.msdn.com/dgoldman/archive/2007/08/23/having-problems-downloading-the-oab-after-you-have-migrated.aspx for more detail.
The general Quest recommendation for accessing mailboxes with a user from different domain is to disable the mailbox object and set the other user to be an associated external account for it.
If both users have to be enabled, there is a potential workaround:
Microsoft have introduced a registry key in Exchange 2003 SP2 that will allow to set a default OAB DN path.
See the following Microsft MSDN blog entry for a very detailed description of the problem and above solution:
Also note that this functionality requires a hotfix if Exchange 2000 is being used, refer to Microsoft KB article ID 842633 "You may receive error messages when you try to download the Offline Address Book on behalf of another user in Exchange 2000 Server" to obtain a hotfix that can be applied to Exchange 2000 Server: