Outlook "My Templates" Add-in Does Not Load Since Latest Exchange Server SU

Question

Hello,

Since installing the latest Exchange Server SU in our environment, the "My Templates" add-in will not load in either the desktop Outlook client or OWA. We have Exchange Server 2019 CU13 running on Windows Server 2019. When the add-in is selected in Outlook, it gives the error: "This add-in could not be started. Close this dialog to ignore the problem or click "Restart" to try again. Clicking "Restart" only refreshes the error.

When I check the event logs on my Exchange server, I see an application warning for ASP.NET any time that Outlook tries to load the add-in:

Event code: 3005 

Event message: An unhandled exception has occurred. 

Event time: 3/25/2024 11:26:50 AM 

Event time (UTC): 3/25/2024 5:26:50 PM 

Event ID: 9359bd0f6de2415897c07681e118f16b 

Event sequence: 43 

Event occurrence: 8 

Event detail code: 0 

 

Application information: 

    Application domain: /LM/W3SVC/2/ROOT/owa-1-133558610081005777 

    Trust level: Full 

    Application Virtual Path: /owa 

    Application Path: C:\Program Files\Microsoft\Exchange Server\V15\ClientAccess\owa\ 

    Machine name: SERVER2019 

 

Process information: 

    Process ID: 11184 

    Process name: w3wp.exe 

    Account name: NT AUTHORITY\SYSTEM 

 

Exception information: 

    Exception type: NullReferenceException 

    Exception message: Object reference not set to an instance of an object.

   at Microsoft.Exchange.Clients.Owa2.Server.Core.OwaModule.ShouldBlockIncomingRequest(HttpContext httpContext)

   at Microsoft.Exchange.Clients.Owa2.Server.Core.OwaModule.OnAuthenticateRequest(Object sender, EventArgs e)

   at System.Web.HttpApplication.SyncEventExecutionStep.System.Web.HttpApplication.IExecutionStep.Execute()

   at System.Web.HttpApplication.ExecuteStepImpl(IExecutionStep step)

   at System.Web.HttpApplication.ExecuteStep(IExecutionStep step, Boolean& completedSynchronously)

 

 

Request information: 

    Request URL: https://<IP address>:444/owa/prem/15.2.1258.32/ext/def/a216ceed-7791-4635-a752-5a4ac0a5eb93/images/app_icon.png 

    Request path: /owa/prem/15.2.1258.32/ext/def/a216ceed-7791-4635-a752-5a4ac0a5eb93/images/app_icon.png 

    User host address: ::1 

    User:  

    Is authenticated: False 

    Authentication Type:  

    Thread account name: NT AUTHORITY\SYSTEM 

 

Thread information: 

    Thread ID: 49 

    Thread account name: NT AUTHORITY\SYSTEM 

    Is impersonating: False 

    Stack trace:    at Microsoft.Exchange.Clients.Owa2.Server.Core.OwaModule.ShouldBlockIncomingRequest(HttpContext httpContext)

   at Microsoft.Exchange.Clients.Owa2.Server.Core.OwaModule.OnAuthenticateRequest(Object sender, EventArgs e)

   at System.Web.HttpApplication.SyncEventExecutionStep.System.Web.HttpApplication.IExecutionStep.Execute()

   at System.Web.HttpApplication.ExecuteStepImpl(IExecutionStep step)

   at System.Web.HttpApplication.ExecuteStep(IExecutionStep step, Boolean& completedSynchronously)

 

 

Custom event details: 

Any insight would be appreciated.

Answer 1

Hi @Nate ,

I understand that the issue with the “My Templates” add-in not loading started after installing the latest Exchange Server Service Update (SU) in your environment.

In order to verify, could you please provide more information?

1. Can you access ECP on the server?
2. what detailed version of Outlook are you using?

Here are some potential solutions based on similar issues reported by others:

1. Internet Explorer Settings: Some users have reported that enabling Internet Explorer in the Control Panel resolved similar issues.
2. Reinstall the Add-in: If possible, try removing and then reinstalling the “My Templates” add-in to see if this resolves the issue.
3. Reinstall the Update: Uninstall and reinstall the update from an administrative command prompt, then reboot the server after the installation is complete.

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Answer 2

I can confirm this issue aswell. A contact told me that this was because of the Security Update that borked this AddIn.

Below are lots of Steps I did - with the assumption that an Office and then Windows Update caused the issue:

( I was about to write my own question so ignore those contextual signs - I just copy pasted it here instead)

This issue started last week around Thuresday (21st March 2024). It somewhat conincides with Windows and/or Office Updates I performed on the sunday before.

(I also found the Steps from Faery Fu-MSFT above in an older article and they did not help)

Based on that my first step was to downgrade the office version back to one where it worked. Since we manage multiple customers I had one to compare and went with

Version 1808 (Build 10405.20015) as instructed by:

https://support.microsoft.com/en-gb/topic/how-to-revert-to-an-earlier-version-of-office-2bd5c457-a917-d57e-35a1-f709e3dda841

and

https://learn.microsoft.com/en-us/officeupdates/update-history-office-2019

The error says: There was an error while trying to reach this AddOn." and affects all users.

Sadly that did not solve the issue, so my next steps were:

• Disable the IE thing mentioed in the linked issue > "May I please confirm that you tried to turn on script debugging in Internet Explorer? to check this kindly Go to Tools > Internet-->Options > Advanced-->Under Browsing uncheck Disable script debugging (Internet Explorer) and Disable script debugging (Other). "
• Delete the Outlook Profile and create a new one - Restart the Computer/Server (Windows Server 2019)
• Update Office again
• Deactivate all PlugIn's and only leave the "Office VBA PlugIn" enabled
• I tried to copy the Outlook VBA.dll from a Server that works and replaced it on this server

Path: C:\Program Files\Microsoft Office\root\Office16\ADDINS\OUTLVBA.dll

I also changed the security settings so that all users have fulkl acess to it

( I changed this back)

• I made sure that within our self-Hosted Exchange the PlugIn is enabled, and turned it off an on again
• I reinstalled office

Uninstalled it trough the system preferenaces pane, deleted the Office Folder, restarted the server and installed it again.

• In "Local USers" Reg Keys I delete the entirety of the OFfice RegKeys and setup Outlook again > Computer\HKEY_CURRENT_USER\SOFTWARE\Microsoft\Office

After some more research I was able to reproduce the issue in Webmail for this Exchange Server. This allowed me to confirm that the issue is NOT with any Windows or Office update which i Had asssumed until that point.

Testing this issue with other Customers a bit later, it seems that those are now affected aswell. From a contact I have with more expertise in Exchange Server I was told that the latest security Update introduced this issue and he was able to reproduce the issue with his Exchange Server. They asked us to "annoy" Microsoft with this and hope they issue a fix soon.

Greetings,

Sam