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Upgrading to Outlook 2003

Does it make sense for you?

Given that a lot of software has reached the stage at which it's "good enough" for most users (many of whom never use more than 20 percent of a product's functionality), software manufacturers often struggle to persuade customers to upgrade to the latest release of their products. Even Microsoft has this problem, notably with well-established products such as Windows, Exchange Server, and Microsoft Office. Currently, many organizations are weighing the decision to upgrade to Office Outlook 2003. The following discussion might make the upgrade choice a bit easier.

Choosing to Upgrade
Outlook is the most common client used in corporate Exchange deployments, but it can also connect to other email servers, including Lotus Domino Server, Oracle Collaboration Server, any IMAP or POP3 server, and any HTTP server that supports WWW Distributed Authoring and Versioning (WebDAV). Indeed, one of Microsoft's challenges is to maintain Outlook's ability to connect to many different email servers while deepening the ability of Exchange and Outlook to work well together. From Microsoft's perspective, it wouldn't make competitive sense for Outlook to work as well with Domino as it does with Exchange, yet until Microsoft released Outlook 2003, the company had never emphasized close collaboration between Outlook and Exchange. The products followed different release cycles and, at times, Microsoft seemed to have more interest in making Outlook an Internet client than in having it make the best use of Exchange. Microsoft's strategy changed with the coordinated release of Windows Server 2003, Exchange Server 2003, and Outlook 2003 because Microsoft wanted customers to view the trio as a set of complementary products designed to work together out of the box. I began using beta versions of Exchange 2003 and Outlook 2003 in late 2002 and have become familiar with their many improvements, some of which are more important to the way I work than others.

Cached Exchange Mode
My favorite new Outlook 2003 feature is Cached Exchange mode, largely because I spend so much time on the road. I can now take along my complete mailbox (plus the Offline Address Book--OAB) and work more effectively than ever before. In Cached Exchange mode, Outlook synchronizes copies of all your mailbox folders (and any public folder favorites that you set up) to the offline folder store (OST). Earlier Outlook versions synchronized only selected folders--usually essential email folders such as the Inbox, Calendar, and Sent Items--to the OST.

The major advantage of having a complete copy of your mailbox in a local file is that you can work locally and remain insulated from any temporary network outages. Earlier versions of Outlook are sensitive to network interruptions, and users can experience frequent hangs as Outlook and Exchange swap remote procedure calls (RPCs) with each other, sometimes unsuccessfully. Outlook with Cached Exchange mode uses as many as four threads to synchronize with your mailbox, so if a mailbox change (such as a new message arriving in the Inbox) occurs on either the client or the server, Outlook can rapidly synchronize both levels. Outlook 2003 maintains a separate high-priority thread for operations that need to happen fast, such as sending messages. Also, if you're working in Cached Exchange mode and the network link fails, you can continue working, and as soon as the network is available again, Outlook automatically connects and synchronizes the mailbox. In earlier Outlook versions, a network failure meant users had to shut down and restart the client.

Smarter Networking
Outlook 2003 boasts many improvements to the way it connects across networks, such as smarter synchronization, attachment compression, and better buffer packing, which means that Outlook 2003 is less "chatty" than earlier versions in the way it communicates with Exchange. (It was always a wonder to me why synchronizing a few messages took so long and generated so much network traffic.) You also have more control over whether Outlook downloads only message headers or full items on different types of connections, as Figure 1 shows. On a DSL-style connection (which Outlook considers fast), you'll probably work as you do on a LAN and select Download Full Items, but you can use other options depending on network responsiveness. Outlook 2003 also displays its current connectivity state and the synchronization status on the status bar.

Outlook 2003 supports drizzle-mode synchronization, which means it downloads header information to the Inbox before it downloads the message body and any attachments. Along with the headers, Outlook downloads the first few lines of content to display in the autopreview pane. Drizzle-mode synchronization (the default setting) lets Outlook synchronize over low-speed, high-latency connections--functionality that's increasingly important as more devices become wireless enabled.

Another synchronization improvement is Outlook's ability to cope with corrupt items that it encounters during the synchronization process. In earlier Outlook versions, these items caused synchronization to hang, but Outlook 2003 skips the corrupt items and synchronizes the rest of the mailbox. Outlook 2003 also handles interruptions better than earlier versions because it starts resynchronizing at the last processed item rather than starting over after an error occurs.

With these networking-related improvements, Outlook 2003 generates less traffic on the wire and synchronization is smoother, but I've found one change that I dislike and that might present problems for some organizations. Outlook 2003 downloads a set of updates for the OAB daily. This behavior has valid reasoning behind it: If you have an outdated OAB, you can't address messages accurately and you might not be able to address some users at all if they don't appear in the copy of the OAB on your PC. However, large organizations might have megabytes of OAB updates that can take a long time to download, and Outlook starts to download the updates without first prompting the user. Fortunately, individuals can disable Outlook's automatic OAB-download behavior by setting the DownloadOAB REG_DWORD value to 0 in the HKEY_CURRENT_USER\Software\Microsoft\Office\11.0\Outlook\Cached Mode registry subkey. The Microsoft article "How to configure how the Offline Address Book is downloaded when you use Outlook 2003 in Cached Exchange Mode" ( discusses this and other options for modifying Outlook 2003's OAB-download behavior.

One other OAB limitation is the inability to see new entries to the Global Address List (GAL) until Exchange incorporates them into the OAB through the OAB-generation process. This process runs on a nominated server nightly (typically at 4:00 a.m.) to build a complete OAB and a differences file, which contains the updates since Exchange built the last OAB. Exchange holds these files in a compressed format in a system public folder that it replicates to other servers within the organization so that clients can download a copy of the OAB from a local server.

It can take 48 hours for new GAL entries to appear in a user's OAB. I'd like to see new functionality whereby Exchange would search the GAL if it didn't find an entry in the OAB, then insert the search results into the OAB. You can modify the registry on a client PC to make Outlook include the online GAL in directory lookups. To do so, create a new REG_DWORD value under the HKEY_CURRENT_USER\Software\Microsoft\Office\11.0\Outlook\Cached Mode subkey, name it ANR Include Online GAL, and set the value to 1. This setting forces Outlook to go to the online GAL (on a Global Catalog--GC--server) for any lookup that is ambiguous (i.e., one that has multiple matches). However, this behavior generates RPCs between the client and server to resolve directory lookups. Not only does this increase network demand, it also increases the time addresses take to resolve.

Today's messaging systems must cope with larger attachments as people use more graphics in their communications. Outlook 2003 can detect that you want to send an attachment and proposes options, which Figure 2 shows, that can reduce network load: for example, sharing attachments in a Windows SharePoint Services workspace. If the attachment is a graphics file, Outlook lets you resize it.

Outlook 2003 also includes better on-the-wire compression of Messaging API (MAPI) RPCs, and Microsoft has tweaked buffer packing. All these changes contribute to fewer bytes flowing across the wires and a generally snappier performance as you work with messages.

Microsoft says that Outlook 2003 clients smooth out network demand because they generate a constant trickle of network requests to synchronize mailboxes rather than the sporadic bursts of activity that earlier Outlook versions generated. For example, you expect to see heavy network activity early in the workday as clients connect to pick up and send messages. You still see heavier demand at this time with Outlook 2003, but the demand is more constant than the peaks and valleys that occurred with previous versions.

Of course, every environment is different, so the following theory might not work well for you, but Microsoft touts Cached Exchange mode and smarter networking as a foundation for server consolidation. The basic argument is that in the past, you placed servers close to user communities to let users keep working during network outages. This setup can result in lots of servers, perhaps one per branch office. The combination of Exchange 2003 and Outlook 2003 permits you to consolidate branch office servers into centralized datacenters. Users shouldn't notice the difference because Outlook (rather than local network connections) protects them against outages.

Unicode OSTs and PSTs
In earlier Outlook versions, OST and personal folder store (PST) files are in ANSI format and suffer from some limitations, most notably a 2GB file-size limit. As messages and attachments grow larger, you need to be able to store them in files that can grow larger than this limit.

The Unicode versions of the OST and PST can grow larger than 2GB; however, good reasons exist for not letting these files grow much larger than 5GB. First, the files aren't very efficient when they grow larger than 2GB, and your hard disk will have to work to keep the OST updated as new mail arrives. Second, the hard disk is often relatively slow on laptop computers, which compounds the internal inefficiency. Third, Microsoft didn't design PSTs and OSTs to cope with today's large volume of data (i.e., both number of messages and file sizes), and corruptions can occur if you attempt to extend PSTs and OSTs too much. The Microsoft article "How to configure the size limit for both .pst and .ost files in Outlook 2003" ( provides details about how to configure the size limits of these files.

Unicode files are a step forward, but they solve only one major problem--file-size limits--so don't expect much more from them. Note that you can't upgrade an OST or PST file to Unicode format. You have to recreate the file from scratch if you want to use the new format (although if you create a new Unicode PST, you can drag folders into it from the old PST).

Junk-Mail Processing
Spam is easily the most irritating aspect of email, so the Junk E-mail Filter in Outlook 2003 is one of that program's most welcome additions. (See "Outlook 2003's Junk E-mail Filter," March 2004, InstantDoc ID 41655, for a more detailed look at this feature.) Fighting spam has become a crusade at Microsoft, with Outlook's Junk E-mail Filter complementing the Spam Confidence Level (SCL) extension in both the Exchange 2003 Store and the Exchange Intelligent Mail Filter (IMF--see "Deploying Exchange Intelligent Message Filter," September 2004, InstantDoc ID 43151, for more information about this tool). Microsoft's comprehensive antispam strategy provides a way to prevent spam from entering an organization--the job of the Exchange IMF; provides a mechanism to mark suspicious messages for future treatment--the role of the SCL; and provides client-side protection to achieve maximum filtering--what Outlook's junk-mail processing does. The Exchange Edge Server, due in mid-2005, will provide additional spam-fighting capabilities.

Outlook's Junk E-mail Filter uses Microsoft SmartScreen technology (which the Exchange IMF also uses) to detect and delete spam, but only if you run Outlook in Cached Exchange mode or download messages to a local PST. Otherwise, the network overhead for Outlook to scan messages in the server mailbox would be too great. Outlook therefore downloads messages and attachments before performing any junk-mail filtering.

The Outlook 2003 kit includes a 1MB file called outfiltr.dat, which holds information that helps the Junk E-mail Filter detect spam. The information ranges from simple tests that identify messages that have pornographic content to more complex tests that look for patterns that spammers use. Any detection technique based on a static data file will become less effective over time as spammers invent new ways to avoid detection. For this reason, Microsoft regularly provides updated filter files at

You can configure Outlook to move spam into the Junk Mail folder in your mailbox. This option lets you check messages at your leisure and detect any false positives (i.e., messages that aren't spam). You can then change your settings accordingly to allow more accurate filtering. Note that the Junk E-mail Filter ignores messages sent within the same Exchange organization because rarely would someone send internal spam.

The SCL is a numeric value that indicates the likelihood that a message is spam. The filtering mechanism uses certain criteria to judge whether a message might be spam and gives each message a weighted value--the SCL. The higher the SCL, the more likely that the message is spam. The Exchange 2003 Store contains an SCL processor that can suppress spam before it's delivered to users' Inboxes, but you first need to use some application (e.g., the Exchange IMF) to set an SCL threshold value that the Store SCL processor uses to determine which messages to suppress. The tool sometimes suppresses messages from people with whom you want to correspond, so the Junk E-mail Filter lets you create a Safe Senders list, which Figure 3 shows. The list specifies people from whom you want to receive mail no matter the message contents.

The Other Stuff
I lump Outlook 2003's other new features into the category of other stuff. Features such as the new reading pane and search folders are useful enhancements, but they haven't made the same difference to the way I work with Outlook that the other improvements have made. The ability to move a reading pane to the right or bottom of the screen is a nice touch, but I can review messages faster by using the autopreview feature, which displays the first couple of lines from each message in the Inbox. Search folders let you set criteria for which you want Outlook to filter messages. Outlook 2003 includes several built-in folders. For example, the For Follow Up folder shows all flagged messages. I organize my mailbox folder structure such that I can usually find the messages I need, so I haven't added any search folders to my mailbox, but other users might find them useful.

Some readers won't agree with my placement of RPC over HTTP--a feature that lets you connect a local Outlook 2003 client to a remote Exchange 2003 server via a Web browser--in the other stuff category. I counter by saying that although RPC over HTTP is useful, it's useful only when you can implement it, and right now (even with the changes in Exchange 2003 Service Pack 1--SP1), administrators often have to expend too much effort to implement RPC over HTTP in production environments. If you want to learn more about this functionality, read "Troubleshooting RPC over HTTP Connections," August 2004, InstantDoc ID 42887 or "Exchange 2003 RPC over HTTP Access," September 2003, InstantDoc ID 39770.

Making the Move
Although Microsoft has tied Outlook 2003 closely to Exchange 2003, you can still benefit from a client upgrade while you plan your server upgrade to Exchange 2003. Certain features depend on Exchange 2003 (or even Windows 2003, as in the case of RPC over HTTP), but some of the most important features, such as Cached Exchange mode and the Junk E-mail Filter, work with Exchange Server 5.5 or later versions. Web Table 1 (, InstantDoc ID 43545) lists Outlook 2003 features and which versions of Exchange they work with.

For me, the two main reasons to upgrade to Outlook 2003 are its networking enhancements and its spam-fighting capabilities. Outlook 2003 offers many other features, some of which will be more important to you than they are to me, but at the end of the day, the features that help you do your job are the most important.

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