Thunderbird and MS Exchange Server 2003

Hi

The IT department in our house changed to Microsoft Exchange Server 
2003. It seems that they didn't installed the IMAP server (connection 
refused on the IMAP ports).

Before updating to the new Exchange Server it was possible to read my 
mails with Thunderbird using an IMAP mail-account (i.e. it was possible 
to access the folders of the IMAP server).

Normaly in our company the user should use Outlook 2000. But for several 
reasons I want to still use Thunderbird ;-)

Which protocol is used by Outlook 2000 to access the Exchange Server and 
is it possible to tell Thunderbird to use the same mechanism for 
accessing the Exchange Server? (I saw some hints about MAPI - is this 
the mechanism used by Outlook to access the Exchange Server?)

Best regards
   Martin