We wanted to make certain that Exchange admins are aware of an Outlook issue which may impact your plans to move to Exchange Server 2013. As discussed in KB:2934750, Outlook 2013 customers who deployed client updates released in November and December of last year may experience a profile migration error post mailbox migration. When this occurs, it might not be possible to use normal Profile Repair options to restore connectivity. Older versions of Outlook, including Outlook 2013 without the November and December updates will function normally. An Outlook update which resolves this issue is nearing completion and being worked with priority to be released as soon as possible. The Exchange team is working closely with the Outlook team to verify the fix.