Previously when doing migrations from 2003 to 2003, or 2000 to 2003 it was possible to migrate a users mailbox without editing a users profile. I have found that the issue is due to the additional administrative group that the Ex2007 server are located in.
I have found the Exchange Profile Update Tool (exprofre) can address this, however I have found that when Exchange is in native-mode the legacyExchangeDN is not changed when the migrate crosses a AG boundary: http://support.microsoft.com/kb/873214
When testing I have had erratic results when migrating mailboxes - sometimes the Outlook profile needs to be updated and sometimes I get 'disconnected' after the mailbox-move it can resolve itself after the Outlook client has been open for ~15 mins.
Does anyone have any recommendations or experiences from encountering these issues? Should a 2003 to 2007 native-mode migrate be as seamless as a 2003-to-2003 migrate?