XADM: Cannot Assign Deny Permission for Global Security Groups on Public Folders

When you assign a "deny" permission for a global security group on a public folder under a non-MAPI top-level hierarchy, you may receive the following error message:

To resolve this issue, set the Allow Expand DL in ACL Data registry value.

WARNING: If you use Registry Editor incorrectly, you may cause serious problems that may require you to reinstall your operating system. Microsoft cannot guarantee that you can solve problems that result from using Registry Editor incorrectly. Use Registry Editor at your own risk.

To set the Allow Expand DL in ACL Data registry value:

1. Start Registry Editor (Regedt32.exe).
2. Locate and click the following key in the registry:
   HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Services\MSExchangeIS\ParametersSystem
3. On the Edit menu, click Add Value, and then add the following registry value:
   Value name: Allow Expand DL in ACL Data
   Data type: REG_DWORD
   Radix: Binary
   Value data: 1
4. Quit Registry Editor.