Don't know if this can be done within Exchange 2007 only but if you're using Outlook you can configure a rule so that the server sends a automatic reply when the account receives a message.
Menu Tools
-> Rules and Alerts
-> New Rule
-> Select "check messages when they arrive" and click "Next"
-> do not select anything in the next window and confirm the warning message that this rule will be applied to every message you receive
-> select "Have server reply using a specific message"
-> Click on "a specific message" to edit the message.
If you want you can add additional recipients to the CC or BCC field.
