Exchange 2003: Forwarding Unresolved Addresses to Upstream Host
To configure Microsoft Exchange Server 2003 to forward emails with addresses that cannot be delivered to the local server:
- Open Exchange System Manager.
- Navigate through Administrative Groups → First Administrative Group → Servers → [Server] → Protocols → SMTP → Default SMTP Virtual Server.
- Click the Messages tab.
- Enter the upstream smarthost at Forward all mail to unresolved recipients to host.
See SBS 2008 Post-Setup Manual Steps to configure similar functionality for Microsoft Exchange Server 2007.