Overview

When installing GFI MailEssentials or upgrading to GFI MailEssentials from an earlier version, the user interface fails to load and encounters the following error:

HTTP Error 503. The service is unavailable.

Additionally, you may notice that the application pool for GFI MailEssentials is stopped and when trying to open the configuration page, Internet Information Services (IIS) will not be able to access the configuration with the following error:

There was an error while performing this operation.

Error: The configuration section 'system.web.extensions' cannot be read because it is missing a section declaration.

Environment

• GFI MailEssentials
• Microsoft Windows 2008
• Internet Information Services (IIS) 7

Root Cause

After installing Microsoft .NET Framework 4, the managed runtime for this version was not registered correctly in the worker process (w3wp.exe).

Resolution

Update Microsoft Windows Server 2008 to Service Pack 2 or later.