Can anyone give me any suggestions on how to accomplish this?

I have a Windows 2000 domain, and several different groups that have a
single Exchange 2003 Public Folder as one of the members. Whenever anyone
sends a message to that group, the message is delivered to all of the
members of the group, including the Public Folder. What I would like to
happen in addition is for an auto-reply to be generated to the sender,
thanking them for their contribution and letting them know that somebody
will be getting back in touch with them.

I had this working when this was Exchange 5.5 by making the Public Folder a
member of a Distribution List, and setting a Folder Assistant rule on the
Public Folder to reply to anyone who sends a message. However, this doesn't
seem to work with Exchange 2003. Any suggestions?