Issue: The Windows event log points to the application pool crashing. It is not clear why the application pool is crashing.
Normally, this happens silently and IIS starts up another process to service requests. However, something has installed the Visual Studio Just-In-Time debugger and so the prompt in the first email is being displayed which is doubly confirmed by the even log entry:
Application popup:
Visual Studio Just-In-Time Debugger: An unhandled win32 exception occurred in w3wp.exe [5712]. Just-In-Time debugging this exception failed with the following error: “No installed debugger has Just-In-Time debugging enabled”.
In Visual Studio, Just-In-Time debugging can be enabled from Tools > Options > Debugging > Just-In-Time.
Just-In-Time debugging should be disabled. There are instructions on disabling Just-In-Time debugging here: https://msdn.microsoft.com/en-us/library/5hs4b7a6.aspx
If Visual Studio is not installed on the system, the instructions for disabling Just-In-Time debugging through the registry will need to be used. Search for “To disable Just-In-Time debugging by editing the registry” in the linked document for those steps.