External MAPI Clients Cannot Connect with RPC (291000)


The information in this article applies to:

  • Microsoft Internet Security and Acceleration Server 2000
This article was previously published under Q291000

SYMPTOMS

When you are using Server Publishing in Internet Security and Acceleration (ISA) Server 2000 to publish an RPC server (by using either the "Any RPC Server" or "Exchange RPC Server" protocol definition), external Microsoft Windows 2000-based clients can connect to the RPC server behind ISA Server 2000, but clients that are running Microsoft Windows NT 4.0, Microsoft Windows 98, Microsoft Windows 95, or Microsoft Windows Millennium Edition (Me) cannot connect. The error message that is received on the client varies depending on the RPC client program that is being used.

CAUSE

ISA Server 2000 includes an RPC Application Filter feature that you can use to publish RPC servers. This RPC Application Filter functionality checks the RPC Fragmentation flags that are set by the external RPC client that is trying to connect to the published RPC server behind ISA Server.

When Windows 2000 sends an RPC packet that is not fragmented, it indicates this by setting the RPC First Fragment and Last Fragment flag so that it equals 0x3. In Windows NT 4.0, Windows 98, Windows 95, and Windows Me, the First Fragment and Last Fragment flag may be set to 0x0, even for RPC packets that are not fragmented. This cause the RPC Application Filter feature to reject these packets.

RESOLUTION

A supported hotfix is now available from Microsoft, but it is only intended to correct the problem that is described in this article. Only apply it to systems that are experiencing this specific problem. This hotfix may receive additional testing. Therefore, if you are not severely affected by this problem, we recommend that you wait for the next service pack that contains this hotfix.

To resolve this problem immediately, contact Microsoft Product Support Services to obtain the fix. For a complete list of Microsoft Product Support Services phone numbers and information about support costs, visit the following Microsoft Web site:

http://support.microsoft.com/contactus/?ws=support

NOTE: In special cases, charges that are ordinarily incurred for support calls may be canceled if a Microsoft Support Professional determines that a specific update will resolve your problem. The typical support costs will apply to additional support questions and issues that do not qualify for the specific update in question.

The English version of this fix should have the following file attributes or later: 
   Date       Time     Version      Size    File name  
   ----------------------------------------------------
   3/19/2001  11:00AM  3.0.1200.59  43,280  Rpcfltr.dll

STATUS

Microsoft has confirmed that this is a problem in the Microsoft products that are listed at the beginning of this article.
Modification Type:MajorLast Reviewed:4/7/2006
Keywords:kbQFE KBHotfixServer kbenv kbISAServ2000sp1fix kbprb KB291000
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