Microsoft KB Archive/281610

= XCCC: Unable to Receive Instant Messages After Logging On Through a Proxy Server or by Using NAT =

PSS ID Number: 281610

Article Last Modified on 10/30/2003

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The information in this article applies to:


 * Microsoft Exchange 2000 Server
 * Microsoft Small Business Server 2000

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This article was previously published under Q281610



SYMPTOMS
Instant Messaging contacts who log on to the Instant Messaging Service through a proxy server or by using network address translation (NAT) can send instant messages to other contacts, but may not be able to receive instant messages. Other Instant Messaging contacts who respond to instant messages from these &quot;external&quot; Instant Messaging contacts receive the following error message in the Instant Messaging window:

The following message could not be delivered to all recipients:

In addition to the error message that is generated in the Instant Messaging window of the Instant Messaging contact, the following error message is logged in the Internet Information Service (IIS) protocol log of the server that is running the Instant Messaging Service:

NOTIFY /instmsg/aliases/ - 500



CAUSE
This behavior can occur if the Instant Messaging Service cannot communicate with an Instant Messaging contact who logs on to the Instant Messaging Service through a proxy server or by using NAT. When an Instant Messaging contact logs on by using one of these methods, the Instant Messaging client registers the client's local area network (LAN) Internet Protocol (IP) address and a dynamic Transmission Control Protocol (TCP) port over 1024. Generally, these IP addresses are either not routable or not resolvable, and as a result, the Instant Messaging Service cannot deliver the message.



RESOLUTION
Instant Messaging clients must have direct connectivity with the server that is running the Instant Messaging Service. To resolve this behavior, establish direct connectivity by using a virtual private network (VPN) or by dialing directly into the server by using Microsoft Remote Access Service (RAS) or Routing and Remote Access.



STATUS
This behavior is by design.



MORE INFORMATION
Exchange 2000 Service Pack 1 (SP1) includes a new feature for the Instant Messaging Service named &quot;Polling&quot; that may provide a work around to this behavior. In addition, the MSN Messenger Service version 3.5 for the Exchange 2000 Instant Messaging client includes support for fixed ports. For additional information, click the article number below to view the article in the Microsoft Knowledge Base:

283022 XCCC: Exchange 2000 Instant Message Polling and Fixed Ports

You can view additional information about virtual private networks in Microsoft Windows 2000 at the following Web site:

http://www.microsoft.com/windows2000/techinfo/reskit/samplechapters/inbe/inbe_vpn_ldgg.asp

Additional query words: exch2kp2w instmsg message not delivered failure poll rras

Keywords: kberrmsg kbprb KB281610

Technology: kbExchange2000Search kbExchange2000Serv kbExchange2000ServSearch kbExchangeSearch kbSBServ2000 kbSBServSearch kbZNotKeyword3

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