Hi,
As far as I'm aware it can't be done using the default exchange protocols, i.e. using the M$ MAPI. If the Exchange server 'Internet Mail Connector' has been set up with imap4 or pop3 you could readily connect with any mail client.
I had this problem at an ex-employer and the only way I got round it was to run ms/outlook under VMware. It probably works under WINE too but I haven't tried that out myself.
Regards