MSN messenger (text only) is possible through Gaim or a Jabber proxy.

Syncing with Exchange is theoretically possible, and if you've got standards-based email access through your Exchange server (i.e. POP3 or IMAP), these are supported out of the box.

For calendar, todo items and contacts, you'll either need to invest in DejaDesktop; or look at opensync alongside the GPE PIM suite.

HTH,

Andrew