In an older hint, I explained how to avoid Mail.App checking Exchange Public Folders by linking the folder to /dev/null. While this tip works to some extent, it was never an ideal solution I was comfortable deploying to all of our Mac users. Recently, this has posed a problem for our Tiger users, who have to click 'OK' multiple times to avoid permission errors when Mail.App tries to poll all of the public folders.
Just recently, I was told of another way to completely remove Exchange Public Folders from appearing when using Mail.App (or any IMAP client). This is not exactly a 'Mac OS X' hint, as it involves making a change in Windows Active Directory. Therefore, you'll have to coordinate with your network administrators and request this change. Since I am also the Network Administrator, I was able to make this change myself ;).
Here's what I did:
Mac OS X Hints
http://hints.macworld.com/article.php?story=20051007051931489