Outlook 2016: “Use Cached Exchange Mode” Option is Grayed Out

Solve a problem where you can’t enable Use Cached Exchange Mode in Microsoft Outlook 2016 because it is grayed out.

Note: This option is only available for accounts that are using Microsoft Exchange. Cached Exchange Mode will be grayed out if you only have POP3 or IMAP accounts in Outlook.

The option is also grayed out if you are using Windows Server with Terminal Services installed. There is no workaround for this without removing Terminal Services from the machine.”

“Use Cached Exchange Mode” is likely disabled because of a Group Policy that is in effect on your computer. If you are on a company network, you might want to contact an administrator to disable it. Otherwise, you can try to enable it yourself.

1. Hold down the Windows key and press “R“.
2. Type “regedit” and click “OK“.
3. Click the plus sign next to HKEY_CURRENT_USER, then navigate to the following:
   • Software
   • Microsoft
   • Office
   • 15.0
   • Outlook
   • OST
4. Right-click the “NoOST” entry on the right and click “Modify“.
5. Give it a value of “0“.
   Note: Some users report that they assign this value to “3” instead of “0”.
6. Restart Outlook and the “Use Exchange Mode” option shouldn’t be grayed out anymore.

If these steps don’t work for you or you are unable to perform these steps, you may want to speak with your systems administrator to see if it can be enabled on the back end.