Most users, especially those will laptops, will want Outlook to operate in Cached mode but you likely don’t want Outlook caching on boardroom / focus room / huddle room / client room computers.  Cache mode copies a large amount of data from the Exchange server to an .OST file on local PC and in a boardroom that:

  1. takes a few minutes users seldom have in a meeting
  2. opens a security hole by putting potentially sensitive email on another computer
  3. take up considerable space, especially if you have hundreds of users

outlook cached mode does not have level targeting gpoSo what you need to do is leave Outlook’s default settings of caching 1 year of mail on the users primary computer but block Outlook caching on shared computers like boardrooms.  The problem is that Outlooks cached mode settings in HKey_Current_User (HKCU) and you need to apply it only to some computers.

To this, you simple need to set ITEM LEVEL TARGETING.  Unfortunately most GPO’s do not have ITEM LEVEL TARGETING as an option and that includes CACHED EXCHANGE MODE GPO.  Fortunately registry changes do and so all you have to figure out is what registry change you need to make.  We have the answer:

  1. Create new or edit an existing GPO
  2. Expand USER CONFIGURATION > PREFERENCES > WINDOWS SETTINGS > REGISTRY
  3. Right click and CREATE NEW
  4. Set Software\Policies\Microsoft\Office\16.0\outlook\ost\  VALUE=NoOST   REG_DWORD=2
  5. Click the COMMON > ITEM-LEVEL TARGETING > TARGETING… (button)
  6. Click NEW and add the condition you want.  In the screen shots below I set it any computer in the OU = KIOSKS

Click on these screen shots to enlarge them


3 Comments

Ben · April 11, 2022 at 9:28 am

Hi Ian,
I tested and indeed the text was correct using the NoOST value set to 2, so it’s the screenshots that aren’t correct.

Ben · April 8, 2022 at 10:51 am

Hello, great article, thank you! In the instructions you say to create a “NoOST” =2 in the path “Software\Policies\Microsoft\Office\16.0\outlook\ost\” but the screen shot shows a value of “SyncWindowSetting” =1 in the path “”Software\Policies\Microsoft\Office\16.0\outlook\Cached Mode”. Which is the correct one. Many thanks!

    Ian Matthews · April 9, 2022 at 9:51 pm

    That is an excellent point but I no longer have access to those machines to check. I have to think the screenshot is correct, but I can’t think of why I would have written the wrong text. Very odd.

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