If the Exchange server has IMAP access open, you can use whatever email client you want. Personally, I use fdm, mutt, and a custom ldap query tool for address resolution. With only 1 meeting a week, I don't much care about the whole calendering thing, though I do also have some automated tools for hooking emailed meetings into KDE's korganizer. Of course, this isn't a solution that many would find palatable.

If going the IMAP route, you can also use Zimbra Desktop. No need for the Zimbra server side of things. Again, though, integration with Exchange calendering is a shortcoming.