Unfortunately, Microsoft excluded support for Exchange 2003 in Office 2011 for Mac. I thought that at least we could get e-mail operational through IMAP to the 2003 server, but found that the inbox subfolders would not show up. I found this article on using Davmail which once installed showed up all the IMAP folders. Davmail.
If you are using Outlook with IMAP to collect your email and running and mdaemon server you may frequently receive the message: Your IMAP server closed the connection. This can occur if you leave the connection idle for too long In Mdaemon go to setup, Default Domain timeouts and check off IMAP NOOP and IDLE.