How do I reject incoming email for unknown users in MS Exchange 2003?
This solution is for Exchange Servers 2003. It is assumed your Exchange system is already setup and configured correctly
- Start the Exchange System Manager
- Select the properties of "Message Delivery" which can be found under the "Global Settings" folder
- Select the "Recipient Filtering" TAB
- Tick the check box labelled "Filter recipients who are not in the Directory" and select OK.
This solution will be prevent backscatter and stop your exchange server processing NDR's (Non-delivery reports) for unknown users.