Cached Exchange Mode is a GREAT feature of Outlook 2003. As you said it makes a local copy of the Exchange Mailbox on the local machine.
This does so much more than just enabling you to work when you are off the network. Enabling this reduces network traffic, creates faster responds time for the Outlook client (especially with large attachments), being able to use the Junk E-mail Filter and being able to work off-line.
When you create a new profile in Outlook 2003 Cached Exchange mode is enabled by default.
When you upgrade from a previous Outlook version with an Exchange mailbox to Outlook 2003 Cached Exchange mode is disabled by default.
This makes it really hard to determine and control remotely whether your clients have Cached Exchange Mode enabled.
<b>Enabling/Disabling Cached Exchange Mode can be controlled though the registry. This allows you to enable/disable it with a simple logon script to create a standard in your organization without the need of forcing the recreation of the entire profile at start-up or visit each client.</b>
Cached Exchange Mode is controlled by the following key;
[HKCU\Software\Microsoft\Windows NT\CurrentVersion\Windows Messaging Subsystem\Profiles\<ProfileName>\13dbb0c8aa05101a9bb000aa002fc45a]
enabled value; 84 01 00 00
enabled with Public Folders/Favorites: 84 05 00 00
disabled value; 04 00 00 00
Please note that the “00036601″ registry key stores more connection settings that just wether or not Cached Exchange Mode is enabled. The values above are taken from a new mail profile with only the Cached Exchange Mode setting changed. If you’re going to deploy this registry key I recommend taking the value from a properly configured machine for your environment