From a thread I’ve took part in, there are currently no settings in the official office 2003/2007 ADM packs to control this setting.
Here’s the registry how to:
For Outlook 2003:
http://support.microsoft.com/kb/948894 1, Click Start, click Run, type regedit, and then click OK. 2, Locate and then click the following registry subkey: HKEY_CURRENT_USERSoftwareMicrosoftOffice11.0OutlookOptionsFolders 3, On the Edit menu, point to New, and then click DWORD Value. 4, Type DisableEditPermissions, and then press ENTER. 5, Right-click DisableEditPermissions, and then click Modify. 6, In the Value data box, type 1, and then click OK. 7, Exit Registry Editor.
For Outlook 2007, that is HKEY_CURRENT_USERSoftwareMicrosoftOffice12.0OutlookOptionsFolders
Manual creation of the ADM is required, i might post it later on.