It is likely that almost everyone in your organization will be an e-mail user. All of those users may require support at some point in time. In most environments, it is critical to maintain service as much as possible to all users. A single user without e-mail may cost the organization large amounts of money and present the organization in a bad light to any outsiders who want to e-mail that user.
Your Exchange 2000 Server environment may be one of the most complicated and diverse of your IT infrastructure. You may have a wide range of different clients, including the following:
MAPI clients (Exchange Client, Outlook 97, Outlook 98, Outlook 2000, and Outlook 2002)
POP3/IMAP4 clients (Outlook, Outlook Express, Netscape ...