MaxUserPort value is 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]  

Topic Last Modified: 2005-11-18

The Microsoft® Exchange Server Analyzer Tool reads the following registry key to determine the maximum value for the TCP ephemeral port:


An ephemeral port is a port that is used briefly.

If the Exchange Server Analyzer finds the value of the MaxUserPort registry key is less than 50000, the Exchange Server Analyzer displays a warning.

The MaxUserPort value specifies the highest port number that TCP can assign when an application requests an available user port from the system. Typically, ephemeral ports are allocated port number 1024 through port number 5000.

By default, Microsoft Windows Server™ 2003 sets the MaxUserPort value to 5000. Microsoft Windows® 2000 does not add the MaxUserPort value to the registry. You can manually add the MaxUserPort value to the registry. However, on Windows Server 2003 and Windows 2000 Server, Exchange Server 2003 sets the default value to 60000. Exchange 2000 Server does not set a value.

It is recommended that you set the MaxUserPort value to 60000. If you set the MaxUserPort value lower than 60000, you may cause Name Service Provider Interface (NSPI) proxy warnings, such as Event 9040. Event 9040 is documented in the following table.

Event ID 9040

Event Category

NSPI Proxy

Event Source


Event Type


Event Description

NSPI Proxy encountered an error while receiving a packet. The target domain controller or the network or a client might be down. The Winsock subsystem returned the error:[0x2746]. The circuit that received this error is being closed.

To correct this warning, set the value of the MaxUserPort registry key to 60000.


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 correct this warning

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

  2. Navigate to: HKLM\SYSTEM\CurrentControlSet\Services\Tcpip\Parameters

  3. Double-click MaxUserPort, set the Value data field to ea60 (Hexadecimal), and then click OK.

  4. Close the registry editor and restart the computer for this setting to take effect.

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" (