Outlook 2003-Features and Improvements

Outlook 2003 ”Features and Improvements

With all pre-Outlook 2003 clients , you could either connect to the Exchange server or work offline using OST files and sync up with the server at periodic intervals. The fundamental goals established by Microsoft during the development of Outlook 2003 were to insulate the client from network connectivity issues, optimize for low bandwidth, reduce round trips, and reduce the load on servers. This is achieved in Outlook 2003 through a combination of cached mode and much smarter replication. Note, however, that the significant improvements made with the amount of data passing over the wire benefits those users who work online as well.

Outlook 2003 allows users to work as they move between different network states without receiving any errors or warnings. This is achieved by building on features such as cached mode, support for Unicode, improved replication, bandwidth profiles, network connection state monitoring, and RPC over HTTP.

Cached Exchange Mode

Cached Exchange mode can actually be considered as an extension of both traditional online and offline modes, depending on how you look at it. In online mode, everything is available to the client from the server. Cached mode could be considered an extension of this in that everything is available to the client, but the vast majority of data is accessed locally from the OST. In offline mode today, you can selectively choose which folders are available and then manually keep this information in synch with the server data. Cached mode could be considered an extension of this in that everything is available and it is automatically kept in synch with the server data.

Certain data cannot be cached and can be accessed only if the client has a connection to the server, such as Free/Busy and delegate access. When running in cached mode, these resources are seamlessly accessed from the server if a connection to the server is available. Cached mode changes the ballpark as far as server performance goes, because the demand changes to that of replication. After data is in the cache, all subsequent access to it is local, and the server is no longer involved. This contrasts with working in online mode today when the server is involved in every action that the user takes ”if a message is read 10 times, the server has to generate that message 10 times, which clearly affects server performance.

Cached mode can be configured for different data replication modes:

• Full items : The same as using send/receive groups today in versions of Outlook prior to Outlook 2003.

• Header mode : New and brings down the header plus the first 256 bytes of the message to give you enough information to determine how you would like to process the message.

• Drizzle mode : Allows you to quickly see all the items in a folder without having to wait for each individual item to synch down, by pulling down the headers first and then synching the full item in the background. This is much more like the traditional online mode. You don't have to wait until the background task is complete to open/read an individual item, because if you attempt to open a header, a foreground task immediately fetches the full contents of the item for you on demand. Note that merely clicking on an item when in drizzle mode is enough to invoke a full download of that item if the reading pane is open . So, if you are dealing with a lot of mail that is in the process of being drizzled down and you just want to browse the items, it might be preferable to use Auto Preview and switch the Reading Pane off.

Unicode Support

Full Unicode support is now available in the OST, offline address book (OAB), and the new personal stores (PST). This is assuming the Exchange server also supports Unicode. Unicode overcomes the limits associated with ANSI and allows all the text and script characters from all of the principal written languages of the world to be represented using a binary code. Currently, the Unicode standard contains 34,168 distinct coded characters derived from 24 supported language scripts. Existing OSTs/PSTs/OAB files are not upgraded to Unicode ”the only possibility is to create new files.

The OAB is also used in cached mode for all primary addressing needs, assuming it has been downloaded to the client. If the client does not have a copy of the OAB, then all addressing will be done using the normal method (proxy via the Exchange server or directly to a GC). It is not immediately obvious which method you are using, so to check, you can look at the properties of the GAL from the Address Book (right-click it and select Properties). The fact that users are not warned anywhere when they do not have an OAB can cause issues if you lose your connection to your Exchange server. Although cached mode will correctly transition to a disconnected state, the OAB has no way of doing so; therefore, problems arise when you try to reply to e-mail messages. To get around this issue, users must explicitly set the working mode to Offline from the File menu to reply to messages. OAB download requests in cached mode are generated once every 24 hours, unlike the offline mode of operation where it is defined as part of the Send/Receive groups.

Also new is Unicode support for the OAB. The Exchange Server generates up to three versions of the OAB ”one for DOS clients and Exchange clients, one for Exchange 5.5 client and pre-Outlook 2003 clients, and one for Outlook 2003 clients.

There is an OAB Version 2 folder for Outlook 97 to Outlook 2003 (non-Unicode) clients and an OAB Version 3a folder for Outlook 2003 Unicode clients. Exchange Server 2003 generates more attributes for the OAB than previous versions in order to support cached mode. For example, the user's "home database" is now included in the OAB, which avoids Outlook having to make unnecessary DS calls when scheduling a meeting with other users. Another example is the provision of the target address property for users who might exist in another forest (contacts) ”if this wasn't populated into the OAB, then unnecessary directory lookups would be performed. Finally, multivalued fields for home and business phone numbers are also now available. Note that these new properties exist only in the new Unicode OAB, so this requires full OAB downloads performed once by each client. If you are using an Exchange Server 2003-generated OAB and Outlook 2003, you will see a different user interface (UI) when viewing an address book item in order to see these new attributes. For example, the home and business fields will show as drop-down lists instead of a single-line text box.

Improved Replication

Several server changes were required to support cached mode because, if replication was not efficient, the benefits of offloading the server access component would be easily lost. MAPI compression has a significant impact on the number of bytes that cross the wire. Compression is supported only when Outlook 2003 talks to an Exchange 2003 server. A new MAPI call is used by Outlook 2003 to request a transfer, and only Exchange Server 2003 understands this call. The compression ratio will vary depending on the type of data being transferred (pure text, HTML compresses better than images, for example). Typically, text and HTML messages compress to 60 “80% of their original size . RTF messages compress to only around 20%, given that they are already in a compressed format. The compression technology is the same technology that AD uses to perform compression of its RPC data when replicating between servers. Compression significantly helps those remote office scenarios where bandwidth is at a premium.

Buffer packing in Outlook 2003 ensures that the buffer size used when requesting data is optimal for the current network connection. However, with compression, the buffer ends up being less full, and therefore multiple requests can be packed into a buffer until it is full. This avoids unnecessary round trips to the server and fully utilizes the buffer.

Best body support introduced in Outlook 2003 means that Outlook client can ask the Exchange server to provide native mode content instead of forcing the server to convert message bodies into RTF. To support older clients that cannot support HTML format messages, Exchange converts to RTF and sends both formats down to the client. This is clearly wasteful if you know that the client can support HTML (HTML being the native format since Outlook XP). Outlook 2003 can now instruct Exchange to just pass the native content down. Not only does this reduce network traffic, but it also relieves a large processing load off the server because messages do not have to be converted. Instead, if the client ever needs to convert the message body format, it can perform the conversion locally rather than going back to the server to request a new copy of the data.