I have an email-enabled public folder that receives emailed user support requests. I want my replies to these requests to use the folder's address as the reply-to address so that users' responses go into the public folder rather than coming to me. Is that possible?
What you want to do is not only possible, but easy. After you create your reply but before you send it, click Options on the Outlook message toolbar. Under Delivery Options, type the folder's email address into the Have replies sent to field or click Select Names to select the folder from the address book. Recipients will see your name as the From address, but when they reply, their replies will be addressed to the folder.
Note that this technique requires no action by the Exchange administrator, so it's a much simpler solution than trying to send email messages using the folder's address as the From address. Sending as a folder requires the administrator to grant your account Send As privileges over the folder.