Sorry, I didn't pick up on your desire for public folder access. This has been a limitation of Apples implementation of EWS since Snow Leopard. For access to that, you might have to use Outlook 2011.
Your suggestion above to go to System Prefs and set up the Exchange account worked, but there is a weird thing happening that I can't figure out nor can our IT department figure out. After I set up the Exchange account via your instructions and then go to Apple Mail, it indeed works on my network at my home. I then go to my office network and it's working but then when I come home it no longer works. It seems like something in the settings have changed and it just hangs. This is the case with both the Apple Mail connection and my MS Outlook connection to the same server. Do you have any ideas about what is going on?
Also regarding your comment on the public folder access. I have Outlook on my Mac, so I can use that for the Shared Calendars. I mainly just want to use Apple Mail to check my office mail.
Thanks for all your help.
The changing settings could be caused by the "auto discover" service, which reconfigures Mail according to whatever the server specifies. It is possible that it is getting confused when on your internal network and is reconfiguring the external server to be he same asa the internal server.
Try looking at the settings when they work, and turn off the auto discover service. Once set, they should stay the same.