Current senario:
Exchange 2013 cu1 coexisting with Exchange 2007 Sp3 RU 10.
problem statement: users migrated to Exchange 2013 from Exchange 2007 are unable to access shared mailbox which is hosted on exchange 2007 server.
users using outlook 2007 with their account configured primarly and additional shared mail boxes account confired in their profile. All permission are in tact. since in Exchange 2007 environment it was working fine.