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On the surface, the Web service architectures appear sim ilar, yet they are vastly different to the developer. Domino uses Notes APIs such as LotusScript, which can be augmented with inline HTML. Exchange relies on HTML and JavaScript, with ActiveX scripts providing a hook on the server side to the underlying messaging services. GroupWise has no Web service customization in this release.

Microsoft Exchange offers the widest range of client options. You're free to choose between a MAPI or POP3 mail client, an NNTP reader for access to public folders, or a Web browser. In fact, you may choose to jump among clients. All of these protocols, plus Lightweight Directory Access Protocol (LDAP) for directory access, are enabled by default and require very little effort on the administrator's part. In contrast, Domino administrators have to enable each user individually, and users are discouraged from moving among clients.

From the full, proprietary Domino client, however, Lotus provides content-delivery features that others lack. Domino provides an offline Web brows er, server caching and content screening. Like Exchange, USENET News can be merged with private discussion databases for transparent access from the native client.

As for administration, Exchange provides the most seamless inte gration to back-end services, enabling open protocols by default. Domino requires additional setup for each Web user. GroupWise has the strength of extending Novell Directory Services (NDS) and being integrated into NWADMIN, but has yet to provide a decent, consolidated administrative platform. All of these products require native clients or direct access to the server for administration.

How might this mix of clients be used? The selection is based on many factors, but we can look at a few scenarios: native desktop clients for permanent employees within a given support domain; MAPI interfaces for folks who have another type of proprietary client; POP and NNTP for contract assignments and temporaries, or those with the right technical savvy who need only basic services; and W eb-browser access for anyone who may travel without a computer, or for any short-term user.

Microsoft Exchange 5.0
With version 5.0, Exchange is becoming a serious Internet-aware messaging system. It's not dramatically different from Version 4, and the integrated applications may not support your chosen operating systems in most functional respects (see "Messaging Standoff," techweb.cmp.com/ nc/710/710f1.html). However, it adds support for a variety of client access protocols. POP3, NNTP, Web access and LDAP are enabled by default. The Internet Mail Service (formerly the Internet Mail Connector) is included at no charge. Web client access is elegantly implemented and easily customized.

Of course, you need a Windows NT infrastructure to use Exchange, and Web browser access relies on NT's IIS. If you have that in place, Exchange is the obvious choice for messaging services. The se additional protocols open access to other platforms. The underlying security for all methods of access is NT challenge/response, so additional access control list directories are not required.

The first major change with Version 5.0 is the new Outlook Desktop In formation Manager client, available only for the 32-bit Windows environments. (The old Exchange client is available for Macintosh, DOS or 16-bit Windows.) Outlook combines e-mail, calendaring and scheduling, contact and task management, journaling and custom forms-based applications in a single interface. It is similar to Novell GroupWise, minus document management.

Exchange 5.0 delivers content to Web browsers via Exchange Web Client, which ships for free. It's an example of an Active Server Pages application, as supported by the NT IIS. Active Server Pages are essentially HTML documents with some built-in ActiveX script code. You can use a variety of scripting languages, including VB Script or JavaScript, as an interface to the underlying Messaging Object Library.