Topic Last Modified: 2005-11-18

The Microsoft® Exchange Server Analyzer Tool reads the following registry key to determine whether remote procedure call (RPC) buffer packing has been disabled:

HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Services\MSExchangeIS\ParametersSystem\Rpc Packing Enabled

If the Exchange Server Analyzer finds that the value data for the Rpc Packing Enabled registry key has been set to 0, the Exchange Server Analyzer displays a non-default configuration message. The Rpc Packing Enabled registry key is disabled when its value data is set to 0.

The value data for the Rpc Packing Enabled registry key is one of three registry entries that administrators can add to configure RPC compression between Microsoft Office Outlook® 2003 and Exchange Server 2003.

Outlook 2003 can request a data buffer of 96 KB. However, after Exchange Server 2003 has compressed the data, the data buffer may be significantly smaller than the amount that Outlook 2003 has requested.

Exchange Server 2003 supports buffer packing to support varying compression rates and to keep buffers full for efficiency.

When the Rpc Packing Enabled registry key is enabled, Exchange Server 2003 continues to add compressed data to the buffer until the buffer is full. For each data request, Outlook 2003 can download significantly more data than earlier versions of Outlook for the following reasons:

The Exchange Server Analyzer reports this configuration for informational purposes only. No action is required. However, you can delete the Rpc Packing Enabled registry key if you want to restore the default configuration. You can also set the data value of the Rpc Packing Enabled registry key to 1 to enable RPC buffer packing.

This article contains information about editing the registry. Before you edit the registry, make sure you understand how to restore the registry if a problem occurs. For information about how to restore the registry, view the "Restore the Registry" Help topic in Regedit.exe or Regedt32.exe.
To restore the default configuration
  1. Open a registry editor, such as Regedit.exe or Regedt32.exe.

  2. Navigate to: HKLM\System\CurrentControlSet\Services\MSExchangeIS\ParametersSystem

    • To delete the entry, delete the Rpc Packing Enabled value.

    • To preserve the entry and enable RPC buffer packing, double-click Rpc Packing Enabled, set the value to 1, and then click OK.

  3. Close the registry editor.

The Microsoft Exchange Information Store service detects the changes in minutes. You do not have to restart the computer.

Before you edit the registry, and for information about how to edit the registry, see the Microsoft Knowledge Base article 256986, "Description of the Microsoft Windows Registry" (

For more information about setting registry keys to configure RPC compression between Outlook clients and Exchange Server 2003, see the Knowledge Base article 825371, "Modify Remote Procedure Call Compression in Exchange Server 2003" (