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Exchange Server update fails to install and rolls back

Ezra Torres 20 Reputation points
2025-11-17T07:18:41.0366667+00:00

I’m having trouble installing the latest Cumulative Update on my on-premises Exchange Server (2016/2019). The setup starts normally, but during the “Mailbox role: Transport service” step it stops, then rolls back the entire update. No clear error appears in the UI.

In the setup logs, I keep seeing entries like:

ERROR: MsiInstallProduct failed with error code 1603
Failed to configure component: Transport service
Prerequisite analysis failed

What else should I check to identify what’s blocking the CU installation

Exchange | Exchange Server | Development
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  1. Steven-N 15,075 Reputation points Microsoft External Staff Moderator
    2025-11-17T08:24:49.88+00:00

    Hi Ezra Torres

    Thank you for reaching out to Microsoft Q&A forum

    Based on my research, this error happens during a CU install, Exchange re‑installs core components. At the Transport service step, the Windows installer (MSI) hits a block, usually a missing prerequisite, pending reboot, locked file, or bad permissions then and returns error 1603.

    Therefore, you can follow the approaches below to check to identify what’s blocking the CU installation:

    1/ Auto‑check for common blockers by Health checker

    # Elevated Exchange Management Shell
Set-ExecutionPolicy RemoteSigned -Scope Process
.\SetupAssist.ps1 -Verbose
.\HealthChecker.ps1

    Link references:

    https://microsoft.github.io/CSS-Exchange/Setup/SetupAssist/

    https://microsoft.github.io/CSS-Exchange/Diagnostics/HealthChecker/

    Note: Microsoft is providing this information as a convenience to you. These sites are not controlled by Microsoft, and Microsoft cannot make any representations regarding the quality, safety, or suitability of any software or information found there. Please ensure that you fully understand the risks before using any suggestions from the above link.

    2/ Read the right log, then re‑run setup

    Open C:\ExchangeSetupLogs\ExchangeSetup.log, search the first error above rollback (often a path/permission in V15\FrontEnd\HttpProxy\owa\auth or a locked file).

    Re‑run the CU elevated, locally mounted ISO:

    Setup.exe /Mode:Upgrade /IAcceptExchangeServerLicenseTerms_DiagnosticDataOFF [/DoNotEnableEP]

    Reboot, run HealthChecker again, then install the latest Security Update (SU) for that CU.

    Link references:

    https://v4.hkg1.meaqua.org/en-us/Exchange/plan-and-deploy/prerequisites

    https://v4.hkg1.meaqua.org/en-us/exchange/plan-and-deploy/post-installation-tasks/security-best-practices/exchange-server-update-faq

    Hope my answer will help you 

    Best regards

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  1. Q&A Assist
    2025-11-17T07:18:54.8433333+00:00
    AI generated content. This question contains an answer created with AI from Q&A Assist. Learn more

    To troubleshoot the installation failure of the Cumulative Update (CU) for your Exchange Server, particularly the error code 1603 during the "Mailbox role: Transport service" step, you can follow these steps:

    1. Check Exchange Services: Ensure that all necessary Exchange services are running before starting the installation. If any services are stopped, start them and set them to start automatically.
    2. Review Setup Logs: Look deeper into the setup logs located in C:\ExchangeSetupLogs. The logs may provide more specific error messages that can help identify the issue.
    3. Disk Space: Verify that there is sufficient disk space on the server where Exchange is installed. Low disk space can cause installation failures.
    4. Antivirus and Firewall: Temporarily disable any antivirus software or firewall settings that might be interfering with the installation process. Ensure that the setup has the necessary permissions to execute.
    5. Run as Administrator: Make sure to run the setup with elevated permissions. Right-click the setup executable and select "Run as administrator".
    6. Windows Installer Service: Ensure that the Windows Installer service is running. You can check this by running services.msc and looking for the Windows Installer service.
    7. Check for Pending Restarts: Sometimes, a pending restart from a previous installation can block new installations. Ensure that there are no pending restarts by checking the system settings or using the command shutdown /a to abort any pending restart.
    8. Use the Setup Log Reviewer: Download and run the SetupLogReviewer.ps1 script to analyze the setup logs and get guidance on resolving the issue.
    9. Prepare Active Directory: If the setup logs indicate issues with Active Directory, ensure that the Exchange organization-level objects are correctly created and that the server is in the same domain as the schema master. You might need to run the setup with the /PrepareAD parameter from a domain-joined machine.

    By following these steps, you should be able to identify and resolve the issues blocking the CU installation for your Exchange Server.

    References:

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