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Troubleshoot Backpressure Triggering

Rousse Jackson 40 Reputation points
2025-12-10T09:47:48.73+00:00

On Exchange Server SE and frequently see backpressure alerts, even though system resources appear healthy. The server temporarily restricts message acceptance, but storage, memory, and CPU are nowhere near the thresholds normally associated with backpressure. Have reviewed the transport settings and disk I/O counters, but not seeing an obvious bottleneck.

What’s the best way to diagnose overly sensitive backpressure behavior in Exchange Server S

Exchange | Exchange Server | Management
Exchange | Exchange Server | Management
The administration and maintenance of Microsoft Exchange Server to ensure secure, reliable, and efficient email and collaboration services across an organization.
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  1. Vergil-V 7,550 Reputation points Microsoft External Staff Moderator
    2025-12-10T12:03:12.28+00:00

    Hi @Rousse Jackson 

    Thank you for reaching out to Microsoft Learn Q&A!  
    To help identify why your Exchange Server is triggering backpressure, I recommend running the following PowerShell command in the Exchange Management Shell: 

    [xml]$bp=Get-ExchangeDiagnosticInfo [-Server <ServerIdentity> ] -Process EdgeTransport -Component ResourceThrottling; $bp.Diagnostics.Components.ResourceThrottling.ResourceTracker.ResourceMeter 

     This output will provide insight into which resource is showing high utilization. undefined

    Additionally, you can review related entries in the Event Viewer logs as suggested in the Q&A Assist. These logs often give more context about the resource behavior. undefined

    One possible reason why backpressure occurs even when storage, memory, and CPU appear well below thresholds is that many resources monitored by backpressure use percentage-based calculations rather than absolute values. This can lead to triggering even when overall system metrics look healthy. 
    For more details, please refer to: Understanding back pressure | Microsoft Learn 

    Additionally, you can review the article Transport database: understand, size and troubleshoot | Microsoft Community Hub. It explains why the transport database mail.que file may grow unexpectedly and provides methods to troubleshoot this issue. 

    I hope this helps clarify your situation. If you have any updates or need further assistance, please feel free to share. 

    If the answer is helpful, please click "Accept Answer" and kindly upvote it. If you have extra questions about this answer, please click "Comment". 

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  1. Q&A Assist
    2025-12-10T09:48:00.1733333+00:00
    AI generated content. This question contains an answer created with AI from Q&A Assist. Learn more

    To diagnose overly sensitive backpressure behavior in Exchange Server, consider the following steps:

    1. Monitor Resource Utilization: Use the Get-ExchangeDiagnosticInfo cmdlet to check the current utilization levels of monitored resources. Pay attention to the values for DatabaseUsedSpace, PrivateBytes, QueueLength, SystemMemory, and disk space metrics. This will help you identify if any resource is being incorrectly flagged as under pressure.
    2. Review Event Logs: Check the event logs for any entries related to backpressure events. Look for Event IDs 15004 (increase in resource utilization) and 15005 (decrease in resource utilization) to understand the fluctuations in resource levels.
    3. Analyze Tarpitting Behavior: If tarpitting is being applied, it may indicate that the server is experiencing temporary spikes in resource usage. Investigate the timing and frequency of these spikes to determine if they correlate with specific operations or workloads.
    4. Check Configuration Settings: Review the transport settings and ensure that they are configured correctly. Sometimes, overly aggressive settings can lead to unnecessary backpressure triggers.
    5. Investigate Disk I/O Performance: Since you mentioned reviewing disk I/O counters, ensure that there are no hidden performance issues. Use performance monitoring tools to analyze disk latency and throughput.
    6. Consider Environmental Factors: Look for external factors that could affect resource utilization, such as network issues or other applications consuming resources on the server.

    By following these steps, you should be able to identify the cause of the overly sensitive backpressure behavior and take appropriate actions to mitigate it.

    References:

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