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