2003/2007.
For Outlook 2003/2007 the location is here:
[HKCU\Software\Microsoft\Windows NT\CurrentVersion\Windows Messaging Subsystem\Profiles\<ProfileName>\13dbb0c8aa05101a9bb000aa002fc45a]
Outlook 2003:
00036601 (REG_BINARY)
enabled value; 84 01 00 00
enabled with Public Folders/Favorites: 84 05 00 00
disabled value; 04 00 00 00
Outlook 2007:
enabled value; 84 19 00 00
enabled with Public Folders/Favorites: 84 05 00 00
disabled value; 04 10 00 00
In the registry it is located in d4c3fff326ad1c498c9982bc456d4c6a in Outlook 2010.
Outlook 2010
Cached Exchange Mode is controlled by the following key;
[HKEY_CURRENT_USER\Software\Microsoft\Windows NT\CurrentVersion\Windows Messaging Subsystem\Profiles\Outlook\d4c3fff326ad1c498c9982bc456d4c6a]
00036601 (REG_BINARY)
enabled value; 84 19 00 00
enabled with Public Folders/Favorites: 84 05 00 00
disabled value; 04 10 00 00
Outlook 2010
enabled value; 84 19 00 00 0x84190000 ; as returned by autoit
enabled with Public Folders/Favorites: 84 05 00 00
disabled value; 04 10 00 00 0x04100000 ; as returned by autoit
Outlook 2003:
enabled value; 84 01 00 00
enabled with Public Folders/Favorites: 84 05 00 00
disabled value; 04 00 00 00
Outlook 2007:
enabled value; 84 19 00 00
enabled with Public Folders/Favorites: 84 05 00 00
disabled value; 04 10 00 00