Office 365 Mail delegation issue in Outlook 2010 client

Hi ,

  We recently went live with Office 365 and our entire organization is using Outlook 2010 client . When I try to delegate the permissions from one user's mailbox to his/her assistant so that he can manage his mails & meetings on behalf of him it doesn't seem to work as expected . I added the user's mailbox to the outlook client but I'm not able to expand the folders .It simply says that it cannot expand the folder .The only workaround we have identified for this at the moment is to grant full permissions on the user's mailbox and that's something which is against our complaince policies . So I would like to know whether this is a known issue or does this have anything to do with Outllook 2010 ? I saw few posts where it says that it's the same behaviour in Outlook 2013 too . So could you please check and clarify on this .