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Upgrading your organization from current versions to Exchange Server SE

The_Exchange_Team's avatar
The_Exchange_Team
Platinum Contributor
Sep 10, 2024
Update 10/22/2025: Addition of two more FAQs. In May 2024, we shared our Exchange Server Roadmap Update and our plans for the future of Exchange Server. Since then, we’ve been asked some questions ...
Updated Oct 22, 2025
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Damon Villar's avatar
Damon Villar
Copper Contributor
Oct 01, 2025

I upgraded my Exchange Server 2019 CU15 running on Windows Server 2022 to Exchange Server Subscription Edition and it said that the operation completed successfully. My event logs are full of warnings and errors. Exchange services arent starting.
The system log shows events like below for each application pool that I have.

Log Name:      System
Source:        Microsoft-Windows-WAS
Date:          10/1/2025 1:49:31 PM
Event ID:      5139
Task Category: None
Level:         Warning
Keywords:      Classic
User:          N/A
Computer:      FvMAIL19
Description:
A listener channel for protocol 'http' in worker process '13220' serving application pool 'MSExchangeOWAAppPool' reported a listener channel failure.  The data field contains the error number.

The application log is showing error events like below:

Log Name:      Application
Source:        Microsoft-Windows-IIS-W3SVC-WP
Date:          10/1/2025 1:54:43 PM
Event ID:      2280
Task Category: None
Level:         Error
Keywords:      Classic
User:          N/A
Computer:      FvMAIL19
Description:
The Module DLL C:\Program Files\Microsoft\Exchange Server\V15\Bin\kerbauth.dll failed to load.  The data is the error.

I did not have these events prior to the upgrade. Any ideas on how to address this?

Thanks

 

  • mrlovett's avatar
    mrlovett
    Copper Contributor
    Oct 06, 2025

    Your Exchange upgrade likely failed to fully copy or register critical files, especially kerbauth.dll, causing IIS and Exchange services to break. You’ll need to manually repair the installation.  This is all based on the EVENT IDs you provided.  Make sure AntiVirus is disabled during this process.

    Here’s a detailed breakdown of what’s happening and how to fix it:

    Root Cause

    • Event ID 2280 (kerbauth.dll failed to load) and Event ID 5139 (listener channel failure) are common after Exchange upgrades when:
      • The upgrade didn’t fully copy all required binaries.
      • IIS modules like kerbauth.dll are missing, corrupted, or misregistered.
      • Application pools (e.g., MSExchangeOWAAppPool) fail due to broken dependencies.

    This is especially common when upgrading from Exchange Server 2019 CU15 to Subscription Edition, as the installer may not properly overwrite or register older components.

    Recommended Fixes

    1. Manually Copy Missing Files

    • From the Exchange Subscription Edition ISO, copy the contents of: \Setup\ServerRoles\Common to: C:\Program Files\Microsoft\Exchange Server\V15\Bin
    • Overwrite any existing files. This ensures all updated binaries (including kerbauth.dll) are present.

    2. Re-register IIS Modules

    • Open Command Prompt as Administrator and run: %windir%\system32\inetsrv\appcmd.exe list modules
      • If KerbauthModule is missing or broken, re-register it: %windir%\system32\inetsrv\appcmd.exe install module /name:KerbauthModule /image:"C:\Program Files\Microsoft\Exchange Server\V15\Bin\kerbauth.dll"

    3. Repair Visual C++ Redistributables

    • Ensure Visual C++ 2012 and 2013 Redistributables are installed. Exchange depends on them.
    • Reinstall both from Microsoft’s official site:
      • https://www.microsoft.com/en-us/download/details.aspx?id=30679
      • https://www.microsoft.com/en-us/download/details.aspx?id=40784

    4. Run Exchange Setup in Recovery Mode

    • From the ISO, run: Setup.exe /Mode:RecoverServer /IAcceptExchangeServerLicenseTerms
      • This will repair broken roles and services without wiping configuration.

    5. Reboot and Reapply Latest Security Updates

    • After recovery, reboot the server.
    • Apply the latest Exchange Server Subscription Edition security updates.

    Optional Checks

    • Run the Exchange HealthChecker.ps1 script from Microsoft to validate prerequisites and detect missing components.
    • Check IIS bindings and ensure no ports (like 443 or 80) are blocked or misconfigured.

    You can download the Exchange Server Health Checker script directly from Microsoft's official GitHub repository:

    🔗 https://github.com/microsoft/CSS-Exchange/tree/main/HealthChecker

    To use it:

    1. Download the HealthChecker.ps1 script from the link above.
    2. Run it in PowerShell as Administrator on your Exchange server.
    3. It will generate a detailed HTML report showing:
      • Exchange version and patch level
      • Missing updates
      • Configuration issues
      • TLS and .NET compatibility
      • Known problems and remediation guidance