Microsoft Exchange Server 5.0 Smoothes the Rough Edges

And expands the range of available clients and embraces many protocols

The first release of Microsoft's enterprise messaging server, Exchange 4.0,was in March 1996. Exchange Server 5.0 seeks to eliminate some rough edges inthe original release, radically expand the available clients, and embrace allsorts of Internet protocols. Too much to do in a single release? Well, ifRelease Candidate 1 (RC1), the currently available beta of Exchange 5.0, is anyindication, Microsoft has done a pretty good job, and the upgrade to Exchange5.0 won't require too much effort.

Microsoft released RC1 in December 1996. It was available from Microsoft'sWeb site, and the company issued several thousand kits. I've run RC1 in aproduction environment since early January and am happy with the code'sstability.

An Internet-Friendly Exchange
Exchange has always supported multiple protocols. The product's core isdesigned around a multiprotocol architecture, enabling support for new protocolswithout dramatic redesign or internal conversions. Exchange 4.0 was equallyhappy to dispatch messages via Messaging API (MAPI), X.400, or Simple MailTransfer Protocol (SMTP), but the increasing success of the Internet meant thatmore work was required to make Exchange Internet friendly. Microsoft has donethat work in Exchange 5.0, which supports Network News Transfer Protocol (NNTP),Secure Sockets Layer (SSL), Lightweight Directory Access Protocol (LDAP), HTML,HTTP, and POP3 for the first time.

The Internet protocol expansion achieves two major goals. First, it allowsa higher degree of interconnectivity with sources of information commonly usedon the Internet. (I'll discuss Exchange 5.0 interconnectivity later.) The secondgoal is to expand the range of Exchange clients and allow more choices. Up tonow, the only available Exchange clients came from Microsoft. These clients wereelegantly engineered and highly functional, but they were often resource-hungry.The need to upgrade desktop hardware to accommodate the Exchange clients impededlarge implementation projects, where the cost of replacing hundreds or thousandsof low-end Windows PCs or Apple Macintoshes surpassed any benefits of installinga new mail system. The problem of how to handle UNIX workstations in an Exchangeenvironment also needed a solution. Microsoft's solution? Use Internet protocolsto enable lightweight clients to connect to Exchange Server.

If you need to cater to low-end hardware bases, you can now deploy POP3software or Web browsers as desktop mail clients. POP3 software, traditionallyavailable as freeware or shareware, gives you many choices on differentplatforms but is limited in functionality: POP3 doesn't recognize concepts suchas server-based folders, public folders, and inbox assistants. (For more onExchange 5.0 support for POP3, see Spyros Sakellariadis, "POP3," March1997.)

The connection between Web browsers and Exchange is much more interestingfrom a technical perspective than the capabilities of the POP3 client anddelivers far more functionality than a POP3 client. You can use any Web browserthat supports HTML frames (e.g., Netscape Navigator 2.0 or Microsoft InternetExplorer--IE--3.0 onwards) to access Exchange and get more than just messages.You can view any private or public folder that you can access and see messagescreated and sent. The LDAP protocol gives Web clients access to the Exchangedirectory. You can execute but not set Inbox assistant rules.

The client interface in Screen 1 is a work of art, built of HTML formattinginstructions, frames, and Java applets (used to create messages or executedirectory look-ups). Although the amount of data that must be transmittedbetween server and client to build such a complete interface can result insluggish responses across congested or low-bandwidth networks, the Web clientcertainly works and delivers lots of functionality.

Active Server Is the Key
The magic connecting Web browsers and Exchange is the Exchange ActiveServer, a new Exchange 5.0 component. The Active Server components layer on topof Internet Information Server (IIS) 3.0, which requires that you installWindows NT 4.0 Service Pack 2 (SP2) on any computer you use to connect Webclients to Exchange. You can run IIS and Exchange on the same computer ordistribute them across multiple systems. The Exchange Active Server is anintermediary between Web clients and Exchange, translating client requests fromHTML into MAPI before transmitting them to Exchange, and then translating theresults back from Exchange into HTML before sending formatted pages back toclients.

The Active Server supports authenticated and nonauthenticated (anonymous)access. Authenticated access is, of course, necessary for users to access thecontents of their private mailbox. Such authentication occurs through anordinary logon procedure. You can use SSL to encrypt the mailbox name andpassword information while the message is en route between client and server.Anonymous access is restricted to public folders, and you can set them up tohave read-only or read-write access for people outside your organization.Anonymous access is not a default privilege. You must adjust the access controllist on each folder to make the contents available to anonymous users and definea shortcut to each folder, as Screen 2 shows. Once you establish the appropriateaccess control, you can publish URLs pointing to documents or other items inpublic folders.

LDAP Support
Exchange 5.0 supports LDAP, but only in query mode, and you cannot use LDAPto connect directories. This function is enough to let the lightweight clientsvalidate mail addresses against anything in the Global Address List (GAL), orsearch the Exchange directory, as Screen 3 shows. System administrators cancustomize LDAP to provide a subset of attributes from the GAL to clients, or toensure the return of a limited number of addresses at any one call. Both stepsmean that clients won't get into trouble when requesting vast quantities ofdirectory data. High-end clients continue to use MAPI for their interaction withthe Exchange directory.

The Clients
The high-end Exchange clients are not immune from change. A new version ofthe standard Exchange client comes with Exchange 5.0, and 32-bit clients can nowconsider installing Outlook, which comes bundled with Office 97 or separately.Outlook and the Exchange clients offer different functionality. For example, theOutlook client can recall an unread message, and the Exchange client can't. Ifyou haven't begun client software deployment for Exchange, your best choice isOutlook because it offers more functionality. However, if you're halfway througha deployment, you have no compelling reason to start over and replace clientswith Outlook. Wait until you're ready for Office 97, and install Outlook then. Aslightly different version of the Outlook client is in the Exchange 5.0 kitbecause Microsoft fixed bugs between the release of Office 97 and Exchange 5.0.If you installed Outlook from the Office 97 kit, upgrade to the Exchangeversion, just to make sure that you're running the latest code. The Exchangeclient for Apple Macintosh is updated, too, and now supports Schedule+.

In comparison with the Microsoft Exchange or Outlook client, Web and POP3clients have a passive relationship with Exchange: Such clients always requestinformation from the server. The server never updates them about changedcircumstances such as a new message. For this reason, Microsoft placed a Checkfor new messages button in the Web client interface.

Although the new POP3 and Web clients are free or shareware, Microsoftlicensing policy clearly states that all clients must possess a Client AccessLicense (CAL) before they can connect to a server. The Microsoft Exchange andOutlook clients are far more functional, so influences such as availablehardware or platforms drive the choice to deploy POP3 or Web clients. You'llnever get a Microsoft Exchange client running on a Solaris or Digital UNIXworkstation, but you can run Netscape. If you don't have large amounts of freesystem resources on a low-end 386, a POP3 client such as Pegasus or Eudora Prowill certainly let users communicate with everyone connected to Exchange.

Public Folder Replication

The Active Server melds Web resources with Exchange. The Internet NewsService lets feeds from Internet newsgroups come directly into a public folder,or has Exchange act as a newsgroup server. Maintaining a single subscription toa newsgroup and using public folder replication to distribute the informationwill usually reduce the amount of data that Internet links must handle, so yougain an immediate advantage. Also, using products like Fulcrum Find! forExchange or Verity's Search97, you can index anything in a public folder easilyfor full text retrieval.

SMTP Support
Microsoft has renamed Exchange 4.0's capable Internet Mail Connector (IMC)to Internet Mail Service (IMS) for Exchange 5.0 and bundles it with all variantsof Exchange server. The IMS can now act as a smart relay host and route new SMTPmessages that are presented to the IMS to other, non-Exchange destinations. Thispoint is important in large messaging environments where you typically operate asingle point of contact (in association with a firewall) between an enterpriseand the Internet. The single point of contact must be able to process messageson behalf of other systems, routing them to their final destination. TheExchange 4.0 IMC did not do this processing, so organizations had to operateanother computer, usually a UNIX system, in that role. Acting as a smart relay,the IMS simplifies operations for all concerned.

SMTP mail systems are less functional (but easier to configure) than theirX.400 equivalents. ESMTP (Extended SMTP) is an attempt by the InternetEngineering Task Force to close the gap, and Exchange 5.0 includes support forRFC 1869 (Delivery Status Notification) and RFC 1870 (Notification of MessageSize). Knowing that a message has reached its destination is clearly important,and Exchange can now fulfill that need if messages are sent to other SMTP mailsystems that support ESMTP.

Setting up IMS is easy with the Internet Setup Wizard. It looks as if theExchange engineers reviewed all the user complaints about the old IMC andattempted to solve the problems by making sure that systems are configuredcorrectly. Anything that sorts out common problems, without a lot of effort fromsystems administrators, is welcome.

Wait, There's More
Exchange 5.0 includes many other changes, so the new version fully justifiesthe new version number (the number allocated to the new version went from 4.1 to4.5, and then to Exchange 5.0, as Microsoft added new features). I'll highlighta few of the more interesting ones.

The Administration program is now easier to use. Common properties (such asthe current logons to the server or the amount of space users occupy in theirmailboxes, as Screen 4 shows) are available with one click, and information isgenerally available faster.

Corporate mail directories can rapidly become so large that knowing whereto look for someone is difficult. Exchange 5.0 supports address book views,virtual containers in the directory that you can create based on differentattributes. For example, if you create a view based on the departmentattribute, Exchange creates containers for each department, such as sales andmarketing.

A competent connector is now available for Lotus cc:Mail. To the cc:Mailenvironment, the connector appears to be just another cc:Mail post office, butthe connector can seamlessly pass messages and directory information betweencc:Mail and Exchange. Interestingly, the cc:Mail connector also lets cc:Mailusers access any other connector Exchange operates, so cc:Mail users can useExchange to route messages to the Internet or X.400, without installing anyother gateways specific to cc:Mail.

Exchange 4.0 included migration utilities to help users of various mailsystems move their data to Exchange. Exchange 5.0 provides new migrationutilities for Netscape Collabra and Novell GroupWise. Some unsupported utilitiesto help migrate UNIX sendmail-type systems are included in the new MicrosoftBackOffice Resource Kit for Microsoft Exchange.

The Exchange 5.0 RC1 requires NT 3.51 SP5 or NT 4.0 SP1. If you want to usethe Active Server to link Web clients, you need IIS 3.0 with the Active Servercomponents, which in turn requires NT 4.0 SP2. The final version of Exchange 5.0will be out by the time you read this, and these requirements might change. Ifyour installation runs Exchange, I recommend you keep up to date with servicepacks for Exchange and NT so you don't have quite so much work when you upgrade.

Beyond Exchange 5.0
The changes in Exchange 5.0 increase the power and flexibility of Exchangeas a messaging platform, chiefly by an impressively seamless integration ofnumerous Internet protocols. Microsoft did not address the weaknesses ofExchange 5.0 groupware capabilities, which make up Exchange's acknowledgedAchilles' heel in comparison to its major competitor, Lotus Notes. Exchangeelectronic forms, for example, are still based in Visual Basic (VB), a languagethat results in slow forms that you can execute only on a Windows platform. Theintroduction of HTML in Exchange 5.0 and the impressive implementation of theWeb client provide a pointer to the future. Microsoft plans to replace VB formswith platform-independent forms built around HTML and ActiveX components,possibly by the end of 1997.

Microsoft sources say we can expect the next version of Exchange in late1997. After all the work to accommodate Internet technologies in Exchange 5.0,the focus of the next release will shift toward the demands of building verylarge servers, those capable of supporting many thousands of users. SomeExchange servers support thousands of users: Digital produces an Alpha serverthat supports 2700 mailboxes. But the challenge is to scale up to 10,000 to20,000 mailboxes. Changes (such as clustering) to achieve truly massivescalability, the ability to support and manage a 16TB information store(Exchange database), and the unification of the Exchange directory with the NTActive Directory (NT 5.0) are needed from both Exchange and the operatingsystem. These developments will help corporate implementation teams, but requirea close eye on what's happening in Exchange and NT over the next few years.