You are using a computer that runs Windows XP® with Service Pack 2. When you attempt to connect to your Exchange server over a MAPI forwarder connection (outlook:// or mapi://), your Outlook client is unable to communicate.
Symptoms Outlook MAPI connections from Windows XP Service Pack 2 You are using a computer that runs Windows XP? with Service Pack 2. When you attempt to connect to your Exchange server over a MAPI forwarder connection (outlook:// or mapi://), your Outlook client is unable to communicate.
Microsoft implemented RPC Interface Restriction in Windows XP Service Pack 2. By default, the update eliminates remote anonymous access to RPC interfaces. the MAPI forwarder creates an anonymous connection to the endpoint mapper (an RPC service).
You can work around this problem in several ways. Some common solutions are:
Enable anonymous RPC connections. This option presents a serious security vulnerability. This configuration change allows any application to connect to the RPC service on your computer. If you use this option, be sure that you implement proper safeguards to protect the computer from external connections. More information on the RPC Interface Restriction is available from Microsoft.
Delay Service Pack 2 roll-out until the problem is resolved.
Configure Exchange to communicate over a specified port range and use TCP tunnels for those ports. Read Microsoft Knowledge Base articles, 270836 and 833799 for more information on this type of configuration.
Configure a Layer 3 VPN profile for access to the Exchange server.