Ran into this issue when launching Outlook 2010 after a USMT migration.
Cannot open your default e-mail folders. The attempt to logon to Microsoft Exchange has failed.
The scenario is a Windows XP SP3 with Office 2003, to Windows 7 SP1 with Office 2010 RTM migration.
User State Migration Toolkit (USMT) 4.0 was used to copy the profile, this included the USMT update to support Office 2010 which can be downloaded here http://support.microsoft.com/kb/2023591
The profile and user settings had migrated successfully, however it appeared that the Outlook profile didn’t migrate.
This is a known issue and an Outlook hotfix is available from Microsoft at the following location.
Once the hotfix is installed the profile opens fine, and all settings are migrated.
This hotfix can be added directly into the task sequence, or into the Office package.
To add into the Office package extract the fix into the updates folder using the following command.
Then copy the two files into the updates folder of the Office 2010 installation sources files
Once you deploy Office 2010 from the updated media, the update will be slipstreamed into the install.
System Center Consultant