Just installed an Exchange 2019 server into an environment that contains two Exchange 2013 servers. The plan is to migrate to 2019 and decommission the 2013 servers. On the new server I am unable to log in to ECP. This is the error I get:

Configuration Error
Description: An error occurred during the processing of a configuration file required to service this request. Please review the specific error details below and modify your configuration file appropriately.

Parser Error Message: Could not load file or assembly 'Microsoft.Exchange.HttpRedirectModules, Version=15.0.0.0, Culture=neutral, PublicKeyToken=31bf3856ad364e35' or one of its dependencies. The system cannot find the file specified.

Source Error:

Line 36: <compilation defaultLanguage="c#" debug="false">
Line 37: <assemblies>
Line 38: <add assembly="Microsoft.Exchange.HttpRedirectModules, Version=15.0.0.0, Culture=neutral, PublicKeyToken=31bf3856ad364e35" />
Line 39: </assemblies>
Line 40: </compilation>

Source File: C:\inetpub\wwwroot\web.config Line: 38

Assembly Load Trace: The following information can be helpful to determine why the assembly 'Microsoft.Exchange.HttpRedirectModules, Version=15.0.0.0, Culture=neutral, PublicKeyToken=31bf3856ad364e35' could not be loaded.

=== Pre-bind state information ===
LOG: DisplayName = Microsoft.Exchange.HttpRedirectModules, Version=15.0.0.0, Culture=neutral, PublicKeyToken=31bf3856ad364e35
(Fully-specified)
LOG: Appbase = file:///C:/inetpub/wwwroot/
LOG: Initial PrivatePath = C:\inetpub\wwwroot\bin

Calling assembly : (Unknown).

LOG: This bind starts in default load context.
LOG: Using application configuration file: C:\inetpub\wwwroot\web.config
LOG: Using host configuration file: C:\Windows\Microsoft.NET\Framework64\v4.0.30319\aspnet.config
LOG: Using machine configuration file from C:\Windows\Microsoft.NET\Framework64\v4.0.30319\config\machine.config.
LOG: Post-policy reference: Microsoft.Exchange.HttpRedirectModules, Version=15.0.0.0, Culture=neutral, PublicKeyToken=31bf3856ad364e35
LOG: Attempting download of new URL file:///C:/Windows/Microsoft.NET/Framework64/v4.0.30319/Temporary ASP.NET Files/root/e22c2559/92c7e946/Microsoft.Exchange.HttpRedirectModules.DLL.
LOG: Attempting download of new URL file:///C:/Windows/Microsoft.NET/Framework64/v4.0.30319/Temporary ASP.NET Files/root/e22c2559/92c7e946/Microsoft.Exchange.HttpRedirectModules/Microsoft.Exchange.HttpRedirectModules.DLL.
LOG: Attempting download of new URL file:///C:/inetpub/wwwroot/bin/Microsoft.Exchange.HttpRedirectModules.DLL.
LOG: Attempting download of new URL file:///C:/inetpub/wwwroot/bin/Microsoft.Exchange.HttpRedirectModules/Microsoft.Exchange.HttpRedirectModules.DLL.
LOG: Attempting download of new URL file:///C:/Windows/Microsoft.NET/Framework64/v4.0.30319/Temporary ASP.NET Files/root/e22c2559/92c7e946/Microsoft.Exchange.HttpRedirectModules.EXE.
LOG: Attempting download of new URL file:///C:/Windows/Microsoft.NET/Framework64/v4.0.30319/Temporary ASP.NET Files/root/e22c2559/92c7e946/Microsoft.Exchange.HttpRedirectModules/Microsoft.Exchange.HttpRedirectModules.EXE.
LOG: Attempting download of new URL file:///C:/inetpub/wwwroot/bin/Microsoft.Exchange.HttpRedirectModules.EXE.
LOG: Attempting download of new URL file:///C:/inetpub/wwwroot/bin/Microsoft.Exchange.HttpRedirectModules/Microsoft.Exchange.HttpRedirectModules.EXE.

Here is what I've tried so far to fix this:

• Confirmed paths are correct in web.config files
• Used DependentAssemblyGenerator.exe to create sharedwebconfig.config in C:\Program Files\Microsoft\Exchange Server\V15\ClientAccess, and C:\Program Files\Microsoft\Exchange Server\V15\FrontEnd\HttpProxy
• I've also done IISReset multiple times as well as rebooted the server

Is there anything else I can do to fix this or should I just open a case with Microsoft support?

Hi @Kenny Stern ,

In order to better solve the problem, I will ask you the following questions:

1. Does the OWA work normally?
2. Have you tried using a different account?
3. Is there any error in event viewer?
4. Use Get-EcpVirtualDirectory to check the EcpVirturalDirectory URL.

5.Did you perform a migration from Exchange 2013 to Exchange 2019?
If the arbitration mailbox is still hosted on an Exchange 2013 server, the following error may occur.
You can move the arbitration mailbox to Exchange 2019 or create a local mailbox on an Exchange 2019 database and assign the Organization Admin role. Then access the ECP again.

Please refer to the following articles:
1 https://learn.microsoft.com/en-us/answers/questions/578660/exchange-2019-ecp-redirects-to-exchange-2013.html
[2] https://learntechfuture.com/2021/08/28/unable-to-login-to-ecp-on-first-exchange-2019-in-exchange-2013-2016-org/

Hi,
Is there any update on this case?
Please let us know if you would like further assistance.
Warm thanks.

Hi

The ECP try to redirect you to the 2013's server. Please try with https://localhost/ecp?ExchClientVer=15.2

In your error code you see Version=15.0.0.0, which is the 2013's version.

That process happen as the admin mailbox is still inside the 2013, it's why Exchange redirect you, but with the tip above you can go in the ecp.

I tried what you suggested but it still gave me the same error.

Thanks, this helped me since we had 2013 and 2019 both in the environment.

Does Exchange Management Shell work fine?

Have you tried recreating the ECP and OWA virtual directories?
The detailed steps are introduced in this link: Recreate virtual directories in Exchange Server.
Please refer to the Recreate EcpVirtualDirectory and Recreate OwaVirtualDirectory part.

Also, check this article for more insight - https://www.stellarinfo.com/blog/exchange-server-http-500-error-ecp/

We've discovered that the virtual directories did not get created in IIS at all. We are working with Microsoft support on the issue.
Thanks for the suggestions.

Hi @Kenny Stern ,

Is there any update on this issue?

Do you mean that you cannot get the ecp virtual directory for Exchange 2019?
If this is the case, it is recommended that you recreate the ECP virtual directory:

New-EcpVirtualDirectory -Server SERVER01 -ExternalURL https://mail.contoso.com/ecp -InternalURL https://mail.contoso.com/ecp