MaxClientRequestBuffer is set too low

[This topic is intended to address a specific issue called out by the Exchange Server Analyzer Tool. You should apply it only to systems that have had the Exchange Server Analyzer Tool run against them and are experiencing that specific issue. The Exchange Server Analyzer Tool, available as a free download, remotely collects configuration data from each server in the topology and automatically analyzes the data. The resulting report details important configuration issues, potential problems, and nondefault product settings. By following these recommendations, you can achieve better performance, scalability, reliability, and uptime. For more information about the tool or to download the latest versions, see "Microsoft Exchange Analyzers" at https://go.microsoft.com/fwlink/?linkid=34707.]  

Topic Last Modified: 2005-11-18

The Microsoft® Exchange Server Analyzer Tool reads the following registry key to determine the value data for the MaxClientRequestBuffer value:

HKEY_LOCAL_MACHINE\System\CurrentControlSet\W3SVC\Parameters\MaxClientRequestBuffer

If the Exchange Server Analyzer finds that the value data for MaxClientRequestBuffer value is lower than 16,384, the Exchange Server Analyzer displays a warning.

If the value for MaxClientRequestBuffer is too low, it could cause errors for Microsoft Office Outlook® Web Access users. Specifically, it could cause HTTP 400 - Bad Request to be returned to the browser. To correct this warning, it is recommended that you either increase the value to a number greater than 16,384 or remove the registry value to revert to the default settings. The MaxClientRequestBuffers value is not present by default.

To correct this warning by increasing the value for the value data

1. Open a registry editor, such as Regedit.exe or Regedt32.exe.

2. Navigate to: HKLM\System\CurrentControlSet\W3SVC\Parameters\MaxClientRequestBuffer

3. Double-click the MaxClientRequestBuffer value and edit the value data. Set the value data to a decimal number that is equal to or greater than 16,384.

4. Close the registry editor and then restart the Exchange server.

To correct this warning by removing the value

1. Open a registry editor, such as Regedit.exe or Regedt32.exe.

2. Navigate to: HKLM\System\CurrentControlSet\W3SVC\Parameters\MaxClientRequestBuffer

3. Right-click the MaxClientRequestBuffer value, and then click Delete.

4. Close the registry editor and restart the Exchange server.

Before you edit the registry, and for information about how to edit the registry, see Microsoft Knowledge Base article 256986, "Description of the Microsoft Windows registry" (https://go.microsoft.com/fwlink/?linkid=3052&kbid=256986).

For more information about the MaxClientRequestBuffer registry value, see Microsoft Knowledge Base article 260694, "Description of the MaxClientRequestBuffer Registry Value" (https://go.microsoft.com/fwlink/?linkid=3052&kbid=260694).