Current Status: Issue with mitigation

Important
With Exchange 2010 SP1 RU3 UDP notifications is being re-added to to Exchange 2010 (read more here). This means that the below symptoms will be resolved, once Exchange 2010 SP1 RU3 becomes available in March 2011.

With Exchange Server 2010, there is no longer support for User Datagram Protocol (UDP) notifications. When opening a mailbox using Outlook 2003, Outlook 2003 tries to register itself to receive new message notifications. By default Outlook 2003 tried to register for UDP notifications but since this notification method isn’t supported with Exchange 2010, Outlook 2003 will instead revert to polling the Exchange server for changes in the mailbox. Despite the fact that Outlook 2003 initiates the polling behavior, the Exchange server will dictate the polling frequency. By default Outlook 2003 polls the Exchange server every 60 seconds.

Since Exchange 2010 doesn’t support UDP based notifications, Outlook 2003 won’t be able to register itself using this method, which means changes made to any of the folders in the mailbox won’t be reflected before Outlook 2003 polls the Exchange server for changes. The result of this is that notifications about new messages etc. will be reflected in the Outlook 2003 client with delays of up to 60 seconds.
More specifically, you will see the following symptoms:

• Outgoing e-mail messages stay in the Outbox for up to 1 minute
• New e-mail messages do not arrive in the Inbox for up to 1 minute
• Items that are deleted from folders do not disappear from the folder for up to 1 minute
• Items that are moved from one folder to another folder take up to 1 minute to disappear from the original folder

Two methods exist to remediate the polling issue described above:

Method 1: Change the Polling Frequency

The issue can be remediated by installing Exchange 2010 Service Pack 1 which includes support for a new registry key that can be used to lower the polling frequency to 5 seconds.

Figure 3: Lowering the polling frequency value

Note
The registry key doesn’t reinstate UDP in Exchange 2010; it only lowers the polling frequency.

Method 2: Enable Cached Mode in Outlook 2003 Clients

The cached mode synchronization process uses a different architecture to update folders versus Outlook 2003 clients in online mode. So another option is to enable cached mode for all Outlook 2003 clients within the organization.

The following KB article describes the symptoms and remediation in detail:

• In Outlook 2003, e-mail messages take a long time to send and receive when you use an Exchange 2010 mailbox

Update: Rollup 3 for Exchange 2010 SP1 is gereleased

Special Thanks to Henrik Walther

Current Status: Issue with mitigation

If the client machine on which Outlook 2003 is installed has been configured to use a proxy server), you must enable "Bypass proxy server for local addresses" under Internet Options > Connections > LAN settings or add the CAS server or CAS arrays to the exception list shown in Figure 10.

Figure 10: Proxy server settings in Internet Explorer

If a proxy server is used in the organization and you haven’t done one of the following:

• Enabled “Bypass proxy server for local addresses”

• Added the CAS server or CAS array to the “Exceptions list”

The Outlook 2003 clients will get an error when trying to download the offline address book (OAB). For more information about the error messages and the steps necessary to remediate the issue, see the following KB article:

• Error message when Outlook synchronizes an offline address book with Exchange Server 2007 and Exchange Server 2010: "0x8004010F"

Note
This issue also affects Outlook 2007 and 2010 clients.

Outlook 2003 clients will also receive an error message when trying to download the OAB if the correct OAB hasn’t been specified for the Exchange 2010 database(s). For more information and steps required to remediate this issue, see the following KB article:

• An error occurs when you try to synchronize the offline address list on an Exchange Server server while you are using Outlook 2003: "0x8004010F"

Special Thanks to Henrik Walther

In some situations Outlook 2003 users connecting to an Exchange mailbox using RPC over HTTP receive the following error message:

“Server Unavailable”

Although this is an Outlook 2003 specific client issue, the issue is not specific for Exchange 2010 organizations. It could also appear in organizations running Exchange 2003 or 2007.

The problem occurs if the RPC proxy server extensions do no load correctly. You can find more details and a description of how the issue can be remediated in the following KB article:

• Error message when Outlook 2003 users connect to an Exchange server by using RPC over HTTP: "Server Unavailable"

Special Thanks to Henrik Walther