You can disable any menu or toolbar command, such as Reply to All, by using a Group Policy Object. The article at
http://www.windowsitpro.com/Article/ArticleID/46342/46342.html explains how.
If you don't want to write your own code to recurse the Explorer.CommandBars
and Inspector.CommandBars collections to get the IDs that you need to be able to disable certain toolbar and menu commands, you can use either the CommandBars
Browser or Outlook Spy tools listed at
http://www.outlookcode.com/d/vb.htm#tools
--
Sue Mosher, Outlook MVP
Author of Configuring Microsoft Outlook 2003
and Microsoft Outlook Programming - Jumpstart for
Administrators, Power Users, and Developers