Unable to access MailEnable webmail via HTTP on Plesk server: HTTP Error 500.24

Symptoms

• Unable to access MailEnable webmail via HTTP, the redirect from HTTP to HTTPS fails with the following error message:

  CONFIG_TEXT: 500 - Internal server error.
  There is a problem with the resource you are looking for, and it cannot be displayed.

• Accessing the MailEnable webmail via HTTP locally from the affected Plesk Windows Server provides more details about the error:

  CONFIG_TEXT: HTTP Error 500.24 - Internal Server Error
  An ASP.NET setting has been detected that does not apply in Integrated managed pipeline mode.
  Most likely causes:
  •system.web/identity@impersonate is set to true.
  ...
  Detailed Error Information:
  Module
  ConfigurationValidationModule
  Notification
  BeginRequest
  Handler
  StaticFile
  Error Code
  0x80070032
  Requested URL
  http://webmail.example.com:80/
  Physical Path
  C:\Program Files (x86)\Plesk\Additional\https-redirect
  Logon Method
  Not yet determined
  Logon User
  Not yet determined

Cause

ASP.NET Impersonation is incompatible with the HTTPS redirect.

IIS Manager > Server > IIS > Authentication > ASP.NET Impersonation is Enabled:

Resolution

1. Connect to the server via RDP

2. Go to IIS Manager > Server > IIS > Authentication:

   

3. Select ASP.NET Impersonation > Click on Disable option located on the right-side Actions menu: