You can't search for admin audit log entries because the arbitration mailbox 'SystemMailbox{e0dc1c29-89c3-4034-b678-e6c29d823ed9}' ...

You can't search for admin audit log entries because the arbitration mailbox 'SystemMailbox{{e0dc1c29-89c3-4034-b678-e6c29d823ed9}}' for the organization '{0}' is located on a server that doesn't have Exchange 2013 installed. The mailbox must be moved to an Exchange 2013 server before you can search for admin audit log entries.