Outlook 2010 | Enable/Disable Cached Exchange Mode | Regedit

If “Cached Exchange Mode” in Outlook is grayed it can be switched on/off via regedit.

To Enable OST files and switch cached exchange mode on:

Windows Registry Editor Version 5.00
[HKEY_CURRENT_USER\Software\Policies\Microsoft\Office\14.0\outlook\ost]
"NoOST"=dword:00000000
[HKEY_CURRENT_USER\Software\Policies\Microsoft\Office\14.0\outlook\cached mode]
"Enable"=dword:00000001

To Disable OST files and switch cached exchange mode off:

Windows Registry Editor Version 5.00
[HKEY_CURRENT_USER\Software\Policies\Microsoft\Office\14.0\outlook\ost]
"NoOST"=dword:00000002
[HKEY_CURRENT_USER\Software\Policies\Microsoft\Office\14.0\outlook\cached mode]
"Enable"=dword:00000000

You can also enabled/disable cached exchange mode for shared mail folders (note this is only slightly different and contained under “Policies”):

Windows Registry Editor Version 5.00
[HKEY_CURRENT_USER\Software\Microsoft\Office\14.0\Outlook\OST]
"NoOST"=dword:00000002
[HKEY_CURRENT_USER\Software\Microsoft\Office\14.0\Outlook\Cached Mode]
"CacheOthersMail"=dword:00000000

Reference: KB982697

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