The Exchange 2007 public folder management interface is quite an improvement over that of previous versions of Exchange. One shortcoming however, is the ability to propagate permissions to subfolders within a public folder. By default, you simply can’t do this in Exchange 2007. In order to accomplish this you must first download the PFDavAdmin tool from Microsoft.
Once downloaded and installed, PFDavAdmin will become your best friend when configuring public folder permissions. Within this utility, simply right click the top level folder whose permissions you which to propagate, choose the Propagate ACE’s option, select the ACE’s you wish to propagate, and click OK.
PFDavAdmin has a few other useful features and should be in the toolkit of any Exchange administrator. You can download this tool here: http://www.microsoft.com/downloads/details.aspx?familyid=635be792-d8ad-49e3-ada4-e2422c0ab424&displaylang=en.