Topic Last Modified: 2010-06-21

The Microsoft Exchange Server 2010 Management Pack for System Center Operations Manager includes a performance data collection engine that is used to query performance counter objects on computers running Exchange 2010. For this Operations Manager rule, data is collected by using the performance counter specified in the Details table.

To review the value of the performance counter that generated this alert, in Operations Manager, double-click this alert, and then click the General tab. Review the description of the alert that includes the variables specific to your environment.


Product Name


Product Version

14.0 (Exchange 2010)

Object Name

MSExchange Throttling Service Client

Counter Name

Percentage of Denied Submission Request.

Sample Interval


Server Role

Ex14. Common

Critical Error Threshold


Rule Path

Microsoft Exchange Server/Exchange 2010/Common Components/Transport Throttling Client

Rule Name

High percentage of transport submissions denied due to Throttling Service Client - sustained for 30 minutes - Red(>10)


This alert indicates that a user has a sustained submission requests that exceed the throttling policy for an extended period.

Microsoft Exchange Server 2010 includes a new feature that is known as throttling. This feature is a framework to which other Exchange 2010 Client Access Server (CAS) components can connect to limit usage of the server's resources. These components include the following:

  • Outlook Web App (OWA)

  • Exchange ActiveSync (EAS)

  • Exchange Web Services (EWS)

  • IMAP4

  • POP3

  • PowerShell

The throttling framework creates a limits-based system that tracks user actions and drops user requests that exceed specified limits. Additionally, the framework provides a way to slow user requests when the CPU usage for a particular CAS component reaches a certain level.

Exchange 2010 throttling may be used to control user access to the following areas:

  • The number of concurrent open connections

  • The time spent connected to a CAS server

  • The time spent performing Active Directory lookup operations and making calls to Active Directory

  • The time spent performing RPC calls to mailbox servers

  • The number of e-mail messages that may be sent

To configure throttling, a group of settings is configured to control how many Exchange resources in the organization are available to a user. This group of settings is known as a throttling policy.

Throttling policies can be used to control only users who connect to Exchange 2010 servers. The policies do not apply to earlier versions of Exchange .

Each setting in a throttling policy has a value. The value represents the amount of access that is given to a user or application for the particular setting. This value is known as the budget.

The performance counters that are used for the MSExchange Throttling Service Client are not used to monitor the Throttling service. Instead, they represent the effectiveness of transport throttling. The Performance counter object that is logged in the "Percentage of Denied Submission Requests" alert represents the percentage of client submission requests that were rejected because the user had exceeded the throttling quota.

Throttled messages remain in the user's Outbox folder until the throttling policy allows the messages to be sent.

User Action

To troubleshoot this issue, determine whether any of the following conditions exist:

  • A program on the user's computer is configured incorrectly. Or, an issues causes the program to try to make too many connections to Exchange  or prevents it from disconnecting from Exchange .

  • The user's computer is running a malicious program.

  • An existing throttling policy is not appropriate for the particular user's requirements.

One or more budget settings in the throttling policy may be set too low to provide the user or the program enough time to complete a required task.

Time settings in a policy are specified as a percentage of one minute. Therefore, a time setting of 100 percent represents 60 seconds. For example, Microsoft Outlook Web App settings in a throttling policy control how long a user can run OWA code against a CAS server together with how long the user can connect to the CAS server. As an example, you may have the following settings configured:

  • OWAPercentTimeInCAS 1

  • OWAPercentTimeInMailboxRPC 1

In this example, the policy settings have a value of 1. This represents one percent of one minute for each setting. Exchange calculates one percent of one minute as 600 milliseconds. Therefore, in this example, the user who is logged on to OWA can access Exchange for up to 600 milliseconds. After this time, the connection becomes over-budget. Exchange 2010 does not allow further access until one minute after the 600 millisecond budget is reached. After this time, the user can again access OWA for 600 milliseconds.

To manage throttling policies in Exchange 2010, use the following cmdlets:

  • Get-ThrottlingPolicy

  • New-ThrottlingPolicy

  • Set-ThrottlingPolicy

  • Remove-ThrottlingPolicy

For More Information

If you are not already doing so, consider running the Exchange tools created to help you analyze and troubleshoot your Exchange environment. These tools can help make sure that your configuration aligns with Microsoft best practices. They can also help you identify and resolve performance issues, improve mail flow, and better manage disaster recovery scenarios. To run these tools, go to the Toolbox node of the Exchange Management Console. To learn more about these tools, see Managing Tools in the Toolbox.

For more information, see Understanding Client Throttling Policies.