The most conventional hosting model is one in which an ISP or application service provider (ASP) offers hosted POP3 and IMAP4 accounts to customers. However, these protocols by themselves don't furnish the goodies you get with Exchange 2000 Server: integrated messaging, shared contacts, calendaring, and so on. You can provide these features to users who run Outlook, but you then encounter bandwidth-allocation and security concerns that are difficult for small or lightweight organizations to address. Outlook Web Access (OWA) provides a nice bridge between these two camps. OWA is automatically installed on Exchange 2000 servers and provides a great deal of useful functionality that's missing from even sophisticated IMAP clients. OWA still isn't quite as full-featured as Outlook, but it's getting closer all the time. And if you run Exchange 2000 Service Pack 2 (SP2) or later, you get quite a bit of flexibility in controlling which individual functions (e.g., calendaring, tasks) users can access. Furthermore, you can—to a degree—customize OWA to control its appearance on users' screens. (Such customization is outside the scope of this article. For more information about the topic, see "Customizing OWA 2000 Access," June 2002, InstantDoc ID 24778.)
